Proxy Serveris
What is a Proxy Server and How Does it Work? – Varonis
The actual nuts and bolts of how the internet works are not something people often stop to consider. The problem with that is the inherent danger of data security breaches and identity theft that come along with the cute dog pictures, 24-hour news updates, and great deals online.
But what actually happens when you browse the web? You might be using a proxy server at your office, on a Virtual Private Network (VPN) or you could be one of the more tech-savvy who always use a proxy server of some kind or another.
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What’s a Proxy Server?
A proxy server is any machine that translates traffic between networks or protocols. It’s an intermediary server separating end-user clients from the destinations that they browse. Proxy servers provide varying levels of functionality, security, and privacy depending on your use case, needs, or company policy.
If you’re using a proxy server, traffic flows through the proxy server on its way to the address you requested. The request then comes back through that same proxy server (there are exceptions to this rule), and then the proxy server forwards the data received from the website to you.
If that’s all it does, why bother with a proxy server? Why not just go straight from to the website and back?
Modern proxy servers do much more than forward web requests, all in the name of data security and network performance. Proxy servers act as a firewall and web filter, provide shared network connections, and cache data to speed up common requests. A good proxy server keeps users and the internal network protected from the bad stuff that lives out in the wild internet. Lastly, proxy servers can provide a high level of privacy.
How Does a Proxy Server Operate?
Every computer on the internet needs to have a unique Internet Protocol (IP) Address. Think of this IP address as your computer’s street address. Just as the post office knows to deliver your mail to your street address, the internet knows how to send the correct data to the correct computer by the IP address.
A proxy server is basically a computer on the internet with its own IP address that your computer knows. When you send a web request, your request goes to the proxy server first. The proxy server then makes your web request on your behalf, collects the response from the web server, and forwards you the web page data so you can see the page in your browser.
When the proxy server forwards your web requests, it can make changes to the data you send and still get you the information that you expect to see. A proxy server can change your IP address, so the web server doesn’t know exactly where you are in the world. It can encrypt your data, so your data is unreadable in transit. And lastly, a proxy server can block access to certain web pages, based on IP address.
What are Forward Proxies
A forward proxy server sits between the client and an external network. It evaluates the outbound requests and takes action on them before relaying that request to the external resource.
Most proxy services that you’re likely to encounter are forward proxies. Virtual Private Networks and Web content filters are both examples of forward proxies.
What are Reverse Proxies
A reverse proxy server sits between a network and multiple other internal resources. A large website might have dozens of servers that collectively serve requests from a single domain. To accomplish that, client requests would resolve to a machine that would act as a load balancer. The load balancer would then proxy that traffic back to the individual servers.
Some popular open source reverse proxies are:
Varnish
Squid
Why Should You Use a Proxy Server?
There are several reasons organizations and individuals use a proxy server.
To control internet usage of employees and children: Organizations and parents set up proxy servers to control and monitor how their employees or kids use the internet. Most organizations don’t want you looking at specific websites on company time, and they can configure the proxy server to deny access to specific sites, instead redirecting you with a nice note asking you to refrain from looking at said sites on the company network. They can also monitor and log all web requests, so even though they might not block the site, they know how much time you spend cyberloafing.
Bandwidth savings and improved speeds: Organizations can also get better overall network performance with a good proxy server. Proxy servers can cache (save a copy of the website locally) popular websites – so when you ask for, the proxy server will check to see if it has the most recent copy of the site, and then send you the saved copy. What this means is that when hundreds of people hit at the same time from the same proxy server, the proxy server only sends one request to This saves bandwidth for the company and improves the network performance.
Privacy benefits: Individuals and organizations alike use proxy servers to browse the internet more privately. Some proxy servers will change the IP address and other identifying information the web request contains. This means the destination server doesn’t know who actually made the original request, which helps keeps your personal information and browsing habits more private.
Improved security: Proxy servers provide security benefits on top of the privacy benefits. You can configure your proxy server to encrypt your web requests to keep prying eyes from reading your transactions. You can also prevent known malware sites from any access through the proxy server. Additionally, organizations can couple their proxy server with a Virtual Private Network (VPN), so remote users always access the internet through the company proxy. A VPN is a direct connection to the company network that companies provide to external or remote users. By using a VPN, the company can control and verify that their users have access to the resources (email, internal data) they need, while also providing a secure connection for the user to protect the company data.
Get access to blocked resources: Proxy servers allow users to circumvent content restrictions imposed by companies or governments. Is the local sportsball team’s game blacked out online? Log into a proxy server on the other side of the country and watch from there. The proxy server makes it look like you are in California, but you actually live in North Carolina. Several governments around the world closely monitor and restrict access to the internet, and proxy servers offer their citizens access to an uncensored internet.
Now that you have an idea about why organizations and individuals use a proxy server, take a look at the risks below.
Proxy Server Risks
You do need to be cautious when you choose a proxy server: a few common risks can negate any of the potential benefits:
Free proxy server risks
You know the old saying “you get what you pay for? ” Well, using one of the many free proxy server services can be quite risky, even the services using ad-based revenue models.
Free usually means they aren’t investing heavily in backend hardware or encryption. You’ll likely see performance issues and potential data security issues. If you ever find a completely “free” proxy server, tread very carefully. Some of those are just looking to steal your credit card numbers.
Browsing history log
The proxy server has your original IP address and web request information possibly unencrypted, saved locally. Make sure to check if your proxy server logs and saves that data – and what kind of retention or law enforcement cooperation policies they follow.
If you expect to use a proxy server for privacy, but the vendor is just logging and selling your data you might not be receiving the expected value for the service.
No encryption
If you use a proxy server without encryption, you might as well not use a proxy server. No encryption means you are sending your requests as plain text. Anyone who is listening will be able to pull usernames and passwords and account information really easily. Make sure whatever proxy server you use provides full encryption capability.
Types of Proxy Servers
Not all proxy servers work the same way. It’s important to understand exactly what functionality you’re getting from the proxy server, and ensure that the proxy server meets your use case.
Transparent Proxy
A transparent proxy tells websites that it is a proxy server and it will still pass along your IP address, identifying you to the web server. Businesses, public libraries, and schools often use transparent proxies for content filtering: they’re easy to set up both client and server side.
Anonymous Proxy
An anonymous proxy will identify itself as a proxy, but it won’t pass your IP address to the website – this helps prevent identity theft and keep your browsing habits private. They can also prevent a website from serving you targeted marketing content based on your location. For example, if knows you live in Raleigh, NC, they will show you news stories they feel are relevant to Raleigh, NC. Browsing anonymously will prevent a website from using some ad targeting techniques, but is not a 100% guarantee.
Distorting proxy
A distorting proxy server passes along a false IP address for you while identifying itself as a proxy. This serves similar purposes as the anonymous proxy, but by passing a false IP address, you can appear to be from a different location to get around content restrictions.
High Anonymity proxy
High Anonymity proxy servers periodically change the IP address they present to the web server, making it very difficult to keep track of what traffic belongs to who. High anonymity proxies, like the TOR Network, is the most private and secure way to read the internet.
Proxy servers are a hot item in the news these days with the controversies around Net Neutrality and censorship. By removing net neutrality protections in the United States, Internet Service Providers (ISP) are now able to control your bandwidth and internet traffic. ISPs can potentially tell you what sites you can and cannot see. While there’s a great amount of uncertainty around what is going to happen with Net Neutrality, it’s possible that proxy servers will provide some ability to work around an ISPs restrictions.
Varonis analyzes data from proxy servers to protect you from data breaches and cyber attacks. The addition of proxy data gives more context to better analyze user behavior trends for abnormalities. You can get an alert on that suspicious activity with actionable intelligence to investigate and deal with the incident.
For example, a user accessing GDPR data might not be significant on its own. But if they access GDPR data and then try to upload it to an external website, it could be an exfiltration attempt and potential data breach. Without the context provided by file system monitoring, proxy monitoring, and Varonis threat models, you might see these events in a vacuum and not realize you need to prevent a data breach.
Get a 1:1 demo to see these threat models in action – and see what your proxy data could be telling you.
Proxy server – Wikipedia
For Wikipedia’s policy on editing from open proxies, please see Wikipedia:Open proxies. For other uses, see Proxy.
Communication between two computers (shown in grey) connected through a third computer (shown in red) which acts as a proxy server. Bob does not know to whom the information is going, which is the reason that proxies can be used to protect privacy.
In computer networking, a proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource. [1]
Instead of connecting directly to a server that can fulfill a requested resource, such as a file or web page, the client directs the request to the proxy server, which evaluates the request and performs the required network transactions. This serves as a method to simplify or control the complexity of the request, or provide additional benefits such as load balancing, privacy, or security. Proxies were devised to add structure and encapsulation to distributed systems. [2] A proxy server thus functions on behalf of the client when requesting service, potentially masking the true origin of the request to the resource server.
Types[edit]
A proxy server may reside on the user’s local computer, or at any point between the user’s computer and destination servers on the Internet. A proxy server that passes unmodified requests and responses is usually called a gateway or sometimes a tunneling proxy. A forward proxy is an Internet-facing proxy used to retrieve data from a wide range of sources (in most cases anywhere on the Internet). A reverse proxy is usually an internal-facing proxy used as a front-end to control and protect access to a server on a private network. A reverse proxy commonly also performs tasks such as load-balancing, authentication, decryption and caching. [3]
Open proxies[edit]
An open proxy forwarding requests from and to anywhere on the Internet.
An open proxy is a forwarding proxy server that is accessible by any Internet user. In 2008, network security expert Gordon Lyon estimates that “hundreds of thousands” of open proxies are operated on the Internet. [4]
Anonymous proxy – This server reveals its identity as a proxy server but does not disclose the originating IP address of the client. Although this type of server can be discovered easily, it can be beneficial for some users as it hides the originating IP address.
Transparent proxy – This server not only identifies itself as a proxy server but with the support of HTTP header fields such as X-Forwarded-For, the originating IP address can be retrieved as well. The main benefit of using this type of server is its ability to cache a website for faster retrieval.
Reverse proxies[edit]
A reverse proxy taking requests from the Internet and forwarding them to servers in an internal network. Those making requests connect to the proxy and may not be aware of the internal network.
A reverse proxy (or surrogate) is a proxy server that appears to clients to be an ordinary server. Reverse proxies forward requests to one or more ordinary servers that handle the request. The response from the proxy server is returned as if it came directly from the original server, leaving the client with no knowledge of the original server. [5] Reverse proxies are installed in the neighborhood of one or more web servers. All traffic coming from the Internet and with a destination of one of the neighborhood’s web servers goes through the proxy server. The use of reverse originates in its counterpart forward proxy since the reverse proxy sits closer to the web server and serves only a restricted set of websites. There are several reasons for installing reverse proxy servers:
Encryption/SSL acceleration: when secure websites are created, the Secure Sockets Layer (SSL) encryption is often not done by the web server itself, but by a reverse proxy that is equipped with SSL acceleration hardware. Furthermore, a host can provide a single “SSL proxy” to provide SSL encryption for an arbitrary number of hosts, removing the need for a separate SSL server certificate for each host, with the downside that all hosts behind the SSL proxy have to share a common DNS name or IP address for SSL connections. This problem can partly be overcome by using the SubjectAltName feature of X. 509 certificates.
Load balancing: the reverse proxy can distribute the load to several web servers, each web server serving its own application area. In such a case, the reverse proxy may need to rewrite the URLs in each web page (translation from externally known URLs to the internal locations).
Serve/cache static content: A reverse proxy can offload the web servers by caching static content like pictures and other static graphical content.
Compression: the proxy server can optimize and compress the content to speed up the load time.
Spoon feeding: reduces resource usage caused by slow clients on the web servers by caching the content the web server sent and slowly “spoon feeding” it to the client. This especially benefits dynamically generated pages.
Security: the proxy server is an additional layer of defense and can protect against some OS and web-server-specific attacks. However, it does not provide any protection from attacks against the web application or service itself, which is generally considered the larger threat.
Extranet publishing: a reverse proxy server facing the Internet can be used to communicate to a firewall server internal to an organization, providing extranet access to some functions while keeping the servers behind the firewalls. If used in this way, security measures should be considered to protect the rest of your infrastructure in case this server is compromised, as its web application is exposed to attack from the Internet.
Uses[edit]
Monitoring and filtering[edit]
Content-control software[edit]
A content-filtering web proxy server provides administrative control over the content that may be relayed in one or both directions through the proxy. It is commonly used in both commercial and non-commercial organizations (especially schools) to ensure that Internet usage conforms to acceptable use policy.
Content filtering proxy servers will often support user authentication to control web access. It also usually produces logs, either to give detailed information about the URLs accessed by specific users or to monitor bandwidth usage statistics. It may also communicate to daemon-based and/or ICAP-based antivirus software to provide security against virus and other malware by scanning incoming content in real-time before it enters the network.
Many workplaces, schools, and colleges restrict web sites and online services that are accessible and available in their buildings. Governments also censor undesirable content. This is done either with a specialized proxy, called a content filter (both commercial and free products are available), or by using a cache-extension protocol such as ICAP, that allows plug-in extensions to an open caching architecture.
Websites commonly used by students to circumvent filters and access blocked content often include a proxy, from which the user can then access the websites that the filter is trying to block.
Requests may be filtered by several methods, such as a URL or DNS blacklists, URL regex filtering, MIME filtering, or content keyword filtering. Blacklists are often provided and maintained by web-filtering companies, often grouped into categories (pornography, gambling, shopping, social networks, etc.. ).
Assuming the requested URL is acceptable, the content is then fetched by the proxy. At this point, a dynamic filter may be applied on the return path. For example, JPEG files could be blocked based on fleshtone matches, or language filters could dynamically detect unwanted language. If the content is rejected then an HTTP fetch error may be returned to the requester.
Most web filtering companies use an internet-wide crawling robot that assesses the likelihood that content is a certain type. The resultant database is then corrected by manual labor based on complaints or known flaws in the content-matching algorithms.
Some proxies scan outbound content, e. g., for data loss prevention; or scan content for malicious software.
Filtering of encrypted data[edit]
Web filtering proxies are not able to peer inside secure sockets HTTP transactions, assuming the chain-of-trust of SSL/TLS (Transport Layer Security) has not been tampered with. The SSL/TLS chain-of-trust relies on trusted root certificate authorities.
In a workplace setting where the client is managed by the organization, devices may be configured to trust a root certificate whose private key is known to the proxy. In such situations, proxy analysis of the contents of an SSL/TLS transaction becomes possible. The proxy is effectively operating a man-in-the-middle attack, allowed by the client’s trust of a root certificate the proxy owns.
Bypassing filters and censorship[edit]
If the destination server filters content based on the origin of the request, the use of a proxy can circumvent this filter. For example, a server using IP-based geolocation to restrict its service to a certain country can be accessed using a proxy located in that country to access the service. [6]: 3
Web proxies are the most common means of bypassing government censorship, although no more than 3% of Internet users use any circumvention tools. [6]: 7
Some proxy service providers allow businesses access to their proxy network for rerouting traffic for business intelligence purposes. [7]
In some cases, users can circumvent proxies which filter using blacklists using services designed to proxy information from a non-blacklisted location. [8]
Many schools block access to popular websites such as Facebook. Students can use proxy servers to circumvent this security. However, by connecting to proxy servers, they might be opening themselves up to danger by passing sensitive information such as personal photos and passwords through the proxy server. Some content filters block proxy servers in order to keep users from using them to bypass the filter.
Logging and eavesdropping[edit]
Proxies can be installed in order to eavesdrop upon the data-flow between client machines and the web. All content sent or accessed – including passwords submitted and cookies used – can be captured and analyzed by the proxy operator. For this reason, passwords to online services (such as webmail and banking) should always be exchanged over a cryptographically secured connection, such as SSL.
By chaining the proxies which do not reveal data about the original requester, it is possible to obfuscate activities from the eyes of the user’s destination. However, more traces will be left on the intermediate hops, which could be used or offered up to trace the user’s activities. If the policies and administrators of these other proxies are unknown, the user may fall victim to a false sense of security just because those details are out of sight and mind.
In what is more of an inconvenience than a risk, proxy users may find themselves being blocked from certain Web sites, as numerous forums and Web sites block IP addresses from proxies known to have spammed or trolled the site. Proxy bouncing can be used to maintain privacy.
Improving performance[edit]
A caching proxy server accelerates service requests by retrieving the content saved from a previous request made by the same client or even other clients. Caching proxies keep local copies of frequently requested resources, allowing large organizations to significantly reduce their upstream bandwidth usage and costs, while significantly increasing performance. Most ISPs and large businesses have a caching proxy. Caching proxies were the first kind of proxy server. Web proxies are commonly used to cache web pages from a web server. [9] Poorly implemented caching proxies can cause problems, such as an inability to use user authentication. [10]
A proxy that is designed to mitigate specific link related issues or degradation is a Performance Enhancing Proxy (PEPs). These are typically used to improve TCP performance in the presence of high round-trip times or high packet loss (such as wireless or mobile phone networks); or highly asymmetric links featuring very different upload and download rates. PEPs can make more efficient use of the network, for example, by merging TCP ACKs (acknowledgements) or compressing data sent at the application layer. [11]
Translation[edit]
A translation proxy is a proxy server that is used to localize a website experience for different markets. Traffic from the global audience is routed through the translation proxy to the source website. As visitors browse the proxied site, requests go back to the source site where pages are rendered. The original language content in the response is replaced by the translated content as it passes back through the proxy. The translations used in a translation proxy can be either machine translation, human translation, or a combination of machine and human translation. Different translation proxy implementations have different capabilities. Some allow further customization of the source site for the local audiences such as excluding the source content or substituting the source content with the original local content.
Repairing errors[edit]
A proxy can be used to automatically repair errors in the proxied content. For instance, the BikiniProxy system instruments JavaScript code on the fly in order to detect and automatically repair errors happening in the browser. [12] Another kind of repair that can be done by a proxy is to fix accessibility issues. [13]
Accessing services anonymously[edit]
An anonymous proxy server (sometimes called a web proxy) generally attempts to anonymize web surfing. Anonymizers may be differentiated into several varieties. The destination server (the server that ultimately satisfies the web request) receives requests from the anonymizing proxy server and thus does not receive information about the end user’s address. The requests are not anonymous to the anonymizing proxy server, however, and so a degree of trust is present between the proxy server and the user. Many proxy servers are funded through a continued advertising link to the user.
Access control: Some proxy servers implement a logon requirement. In large organizations, authorized users must log on to gain access to the web. The organization can thereby track usage to individuals. Some anonymizing proxy servers may forward data packets with header lines such as HTTP_VIA, HTTP_X_FORWARDED_FOR, or HTTP_FORWARDED, which may reveal the IP address of the client. Other anonymizing proxy servers, known as elite or high-anonymity proxies, make it appear that the proxy server is the client. A website could still suspect a proxy is being used if the client sends packets that include a cookie from a previous visit that did not use the high-anonymity proxy server. Clearing cookies, and possibly the cache, would solve this problem.
QA geotargeted advertising[edit]
Advertisers use proxy servers for validating, checking and quality assurance of geotargeted ads. A geotargeting ad server checks the request source IP address and uses a geo-IP database to determine the geographic source of requests. [14] Using a proxy server that is physically located inside a specific country or a city gives advertisers the ability to test geotargeted ads.
Security[edit]
A proxy can keep the internal network structure of a company secret by using network address translation, which can help the security of the internal network. [15] This makes requests from machines and users on the local network anonymous. Proxies can also be combined with firewalls.
An incorrectly configured proxy can provide access to a network otherwise isolated from the Internet. [4]
Cross-domain resources[edit]
Proxies allow web sites to make web requests to externally hosted resources (e. g. images, music files, etc. ) when cross-domain restrictions prohibit the web site from linking directly to the outside domains. Proxies also allow the browser to make web requests to externally hosted content on behalf of a website when cross-domain restrictions (in place to protect websites from the likes of data theft) prohibit the browser from directly accessing the outside domains.
Malicious usages[edit]
Secondary market brokers[edit]
Secondary market brokers use web proxy servers to buy large stocks of limited products such as limited sneakers[16] or tickets.
Implementations of proxies[edit]
Web proxy servers[edit]
Web proxies forward HTTP requests. The request from the client is the same as a regular HTTP request except the full URL is passed, instead of just the path. [17]
GET HTTP/1. 1
Proxy-Authorization: Basic encoded-credentials
Accept: text/html
This request is sent to the proxy server, the proxy makes the request specified and returns the response.
HTTP/1. 1 200 OK
Content-Type: text/html; charset UTF-8
Some web proxies allow the HTTP CONNECT method to set up forwarding of arbitrary data through the connection; a common policy is to only forward port 443 to allow HTTPS traffic.
Examples of web proxy servers include Apache (with mod_proxy or Traffic Server), HAProxy, IIS configured as proxy (e. g., with Application Request Routing), Nginx, Privoxy, Squid, Varnish (reverse proxy only), WinGate, Ziproxy, Tinyproxy, RabbIT and Polipo.
For clients, the problem of complex or multiple proxy-servers is solved by a client-server Proxy auto-config protocol (PAC file).
SOCKS proxy[edit]
SOCKS also forwards arbitrary data after a connection phase, and is similar to HTTP CONNECT in web proxies.
Transparent proxy[edit]
Also known as an intercepting proxy, inline proxy, or forced proxy, a transparent proxy intercepts normal application layer communication without requiring any special client configuration. Clients need not be aware of the existence of the proxy. A transparent proxy is normally located between the client and the Internet, with the proxy performing some of the functions of a gateway or router. [18]
RFC 2616 (Hypertext Transfer Protocol—HTTP/1. 1) offers standard definitions:
“A ‘transparent proxy’ is a proxy that does not modify the request or response beyond what is required for proxy authentication and identification”. “A ‘non-transparent proxy’ is a proxy that modifies the request or response in order to provide some added service to the user agent, such as group annotation services, media type transformation, protocol reduction, or anonymity filtering”.
TCP Intercept is a traffic filtering security feature that protects TCP servers from TCP SYN flood attacks, which are a type of denial-of-service attack. TCP Intercept is available for IP traffic only.
In 2009 a security flaw in the way that transparent proxies operate was published by Robert Auger, [19] and the Computer Emergency Response Team issued an advisory listing dozens of affected transparent and intercepting proxy servers. [20]
Purpose[edit]
Intercepting proxies are commonly used in businesses to enforce acceptable use policy, and to ease administrative overheads since no client browser configuration is required. This second reason however is mitigated by features such as Active Directory group policy, or DHCP and automatic proxy detection.
Intercepting proxies are also commonly used by ISPs in some countries to save upstream bandwidth and improve customer response times by caching. This is more common in countries where bandwidth is more limited (e. island nations) or must be paid for.
Issues[edit]
The diversion/interception of a TCP connection creates several issues. First, the original destination IP and port must somehow be communicated to the proxy. This is not always possible (e. g., where the gateway and proxy reside on different hosts). There is a class of cross-site attacks that depend on certain behavior of intercepting proxies that do not check or have access to information about the original (intercepted) destination. This problem may be resolved by using an integrated packet-level and application level appliance or software which is then able to communicate this information between the packet handler and the proxy.
Intercepting also creates problems for HTTP authentication, especially connection-oriented authentication such as NTLM, as the client browser believes it is talking to a server rather than a proxy. This can cause problems where an intercepting proxy requires authentication, then the user connects to a site that also requires authentication.
Finally, intercepting connections can cause problems for HTTP caches, as some requests and responses become uncacheable by a shared cache.
Implementation methods[edit]
In integrated firewall/proxy servers where the router/firewall is on the same host as the proxy, communicating original destination information can be done by any method, for example Microsoft TMG or WinGate.
Interception can also be performed using Cisco’s WCCP (Web Cache Control Protocol). This proprietary protocol resides on the router and is configured from the cache, allowing the cache to determine what ports and traffic is sent to it via transparent redirection from the router. This redirection can occur in one of two ways: GRE tunneling (OSI Layer 3) or MAC rewrites (OSI Layer 2).
Once traffic reaches the proxy machine itself interception is commonly performed with NAT (Network Address Translation). Such setups are invisible to the client browser, but leave the proxy visible to the web server and other devices on the internet side of the proxy. Recent Linux and some BSD releases provide TPROXY (transparent proxy) which performs IP-level (OSI Layer 3) transparent interception and spoofing of outbound traffic, hiding the proxy IP address from other network devices.
Detection[edit]
Several methods may be used to detect the presence of an intercepting proxy server:
By comparing the client’s external IP address to the address seen by an external web server, or sometimes by examining the HTTP headers received by a server. A number of sites have been created to address this issue, by reporting the user’s IP address as seen by the site back to the user on a web page. Google also returns the IP address as seen by the page if the user searches for “IP”.
By comparing the result of online IP checkers when accessed using HTTPS vs HTTP, as most intercepting proxies do not intercept SSL. If there is suspicion of SSL being intercepted, one can examine the certificate associated with any secure web site, the root certificate should indicate whether it was issued for the purpose of intercepting.
By comparing the sequence of network hops reported by a tool such as traceroute for a proxied protocol such as (port 80) with that for a non-proxied protocol such as SMTP (port 25). [21]
By attempting to make a connection to an IP address at which there is known to be no server. The proxy will accept the connection and then attempt to proxy it on. When the proxy finds no server to accept the connection it may return an error message or simply close the connection to the client. This difference in behavior is simple to detect. For example, most web browsers will generate a browser created error page in the case where they cannot connect to an HTTP server but will return a different error in the case where the connection is accepted and then closed. [22]
By serving the end-user specially programmed Adobe Flash SWF applications or Sun Java applets that send HTTP calls back to their server.
CGI proxy[edit]
A CGI web proxy accepts target URLs using a Web form in the user’s browser window, processes the request, and returns the results to the user’s browser. Consequently, it can be used on a device or network that does not allow “true” proxy settings to be changed. The first recorded CGI proxy, named “rover” at the time but renamed in 1998 to “CGIProxy”, [23] was developed by American computer scientist James Marshall in early 1996 for an article in “Unix Review” by Rich Morin. [24]
The majority of CGI proxies are powered by one of CGIProxy (written in the Perl language), Glype (written in the PHP language), or PHProxy (written in the PHP language). As of April 2016, CGIProxy has received about 2 million downloads, Glype has received almost a million downloads, [25] whilst PHProxy still receives hundreds of downloads per week. [26] Despite waning in popularity[27] due to VPNs and other privacy methods, as of September 2021 there are still a few hundred CGI proxies online. [28]
Some CGI proxies were set up for purposes such as making websites more accessible to disabled people, but have since been shut down due to excessive traffic, usually caused by a third party advertising the service as a means to bypass local filtering. Since many of these users don’t care about the collateral damage they are causing, it became necessary for organizations to hide their proxies, disclosing the URLs only to those who take the trouble to contact the organization and demonstrate a genuine need. [29]
Suffix proxy[edit]
A suffix proxy allows a user to access web content by appending the name of the proxy server to the URL of the requested content (e. “”). Suffix proxy servers are easier to use than regular proxy servers but they do not offer high levels of anonymity and their primary use is for bypassing web filters. However, this is rarely used due to more advanced web filters.
Tor onion proxy software[edit]
Tor is a system intended to provide online anonymity. [30] Tor client software routes Internet traffic through a worldwide volunteer network of servers for concealing a user’s computer location or usage from someone conducting network surveillance or traffic analysis. Using Tor makes tracing Internet activity more difficult, [30] and is intended to protect users’ personal freedom, privacy.
“Onion routing” refers to the layered nature of the encryption service: The original data are encrypted and re-encrypted multiple times, then sent through successive Tor relays, each one of which decrypts a “layer” of encryption before passing the data on to the next relay and ultimately the destination. This reduces the possibility of the original data being unscrambled or understood in transit. [31]
I2P anonymous proxy[edit]
The I2P anonymous network (‘I2P’) is a proxy network aiming at online anonymity. It implements garlic routing, which is an enhancement of Tor’s onion routing. I2P is fully distributed and works by encrypting all communications in various layers and relaying them through a network of routers run by volunteers in various locations. By keeping the source of the information hidden, I2P offers censorship resistance. The goals of I2P are to protect users’ personal freedom, privacy, and ability to conduct confidential business.
Each user of I2P runs an I2P router on their computer (node). The I2P router takes care of finding other peers and building anonymizing tunnels through them. I2P provides proxies for all protocols (HTTP, IRC, SOCKS,… ).
Comparison to network address translators[edit]
The proxy concept refers to a layer 7 application in the OSI reference model. Network address translation (NAT) is similar to a proxy but operates in layer 3.
In the client configuration of layer-3 NAT, configuring the gateway is sufficient. However, for the client configuration of a layer 7 proxy, the destination of the packets that the client generates must always be the proxy server (layer 7), then the proxy server reads each packet and finds out the true destination.
Because NAT operates at layer-3, it is less resource-intensive than the layer-7 proxy, but also less flexible. As we compare these two technologies, we might encounter a terminology known as ‘transparent firewall’. Transparent firewall means that the proxy uses the layer-7 proxy advantages without the knowledge of the client. The client presumes that the gateway is a NAT in layer 3, and it does not have any idea about the inside of the packet, but through this method, the layer-3 packets are sent to the layer-7 proxy for investigation.
DNS proxy[edit]
A DNS proxy server takes DNS queries from a (usually local) network and forwards them to an Internet Domain Name Server. It may also cache DNS records.
Proxifiers[edit]
Some client programs “SOCKS-ify” requests, [32] which allows adaptation of any networked software to connect to external networks via certain types of proxy servers (mostly SOCKS).
Residential proxy[edit]
A residential proxy is an intermediary that uses a real IP address provided by an Internet Service Provider (ISP) with physical devices such as mobiles and computers of end-users. Instead of connecting directly to a server, residential proxy users connect to the target through residential IP addresses. The target then identifies them as organic internet users. It does not let any tracking tool identify the reallocation of the user. Any residential proxy can send any number of concurrent requests and IP addresses are directly related to a specific region. [33]
See also[edit]
Darknet
SMTP proxy
Web accelerator which discusses host-based HTTP acceleration
Web cache
Application firewall
Captive portal
Distributed Checksum Clearinghouse
Internet privacy
Proxy list
SOCKS an alternative firewall traversal protocol supported by many applications
References[edit]
^ World-Wide Web Proxies, Ari Luotonen, April 1994
^ [1], Marc Shapiro. Structure and Encapsulation in Distributed Systems: the Proxy Principle. Int. Conf. on Distr. Comp. Sys. (ICDCS), 1986, Cambridge, MA, USA, United States. pp. 198–204, 1986, Int. (ICDCS).
^ “Proxy servers and tunneling”. MDN Web Docs. Retrieved 6 December 2020.
^ a b Lyon, Gordon (2008). Nmap network scanning. US: Insecure. p. 270. ISBN 978-0-9799587-1-7.
^ “Forward and Reverse Proxies”. d mod_proxy. Apache. Retrieved 20 December 2010.
^ a b “2010 Circumvention Tool Usage Report” (PDF). The Berkman Center for Internet & Society at Harvard University. October 2010.
^ “How to Check if Website is Down or Working Worldwide”. Hostinger. 19 November 2019. Retrieved 14 December 2019.
^ “Using a Ninjaproxy to get through a filtered proxy”. advanced filtering mechanics. TSNP. Archived from the original on 9 March 2016. Retrieved 17 September 2011.
^ Thomas, Keir (2006). Beginning Ubuntu Linux: From Novice to Professional. Apress. ISBN 978-1-59059-627-2. A proxy server helps speed up Internet access by storing frequently accessed pages
^ I. Cooper; J. Dilley (June 2001). Known HTTP Proxy/Caching Problems. IETF. doi:10. 17487/RFC3143. RFC 3143. Retrieved 17 May 2019.
^ “Layering”. Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations. June 2001. p. 4. sec. 2. 1. 17487/RFC3135. RFC 3135. Retrieved 21 February 2014.
^ Durieux, T. ; Hamadi, Y. ; Monperrus, M. (2018). Fully Automated HTML and JavaScript Rewriting for Constructing a Self-Healing Web Proxy. 2018 IEEE 29th International Symposium on Software Reliability Engineering (ISSRE). pp. 1–12. arXiv:1803. 08725. 1109/ISSRE. 2018. 00012. ISBN 978-1-5386-8321-7. S2CID 4268784.
^ Zhang, Xiaoyi; Ross, Anne Spencer; Caspi, Anat; Fogarty, James; Wobbrock, Jacob O. (2017). Interaction Proxies for Runtime Repair and Enhancement of Mobile Application Accessibility. Proceedings of the 2017 CHI Conference on Human Factors in Computing Systems. pp. 6024–6037. 1145/3025453. 3025846. ISBN 9781450346559. S2CID 20937177.
^ “Hot Tactics For Geo-Targeted Ads on Google & Bing”. Retrieved 7 February 2014.
^ “Firewall and Proxy Server HOWTO”. Retrieved 4 September 2011. The proxy server is, above all, a security device.
^ “Sneaker Bot Supreme Proxy”. GeoSurf. Retrieved 24 September 2017.
^ “absolute-form”. HTTP/1. 1 Message Syntax and Routing. June 2014. p. 41. sec. 5. 3. 2. 17487/RFC7230. RFC 7230. Retrieved 4 November 2017. a client MUST send the target URI in absolute-form as the request-target
^ “Transparent Proxy Definition”. 1 February 2011. Archived from the original on 1 March 2013. Retrieved 14 February 2013.
^ “Socket Capable Browser Plugins Result in Transparent Proxy Abuse”. The Security Practice. 9 March 2009. Retrieved 14 August 2010.
^ “Vulnerability Note VU#435052”. US CERT. 23 February 2009. Retrieved 14 August 2010.
^ “Subversion Dev: Transparent Proxy detection (was Re: Introduction_”. Retrieved 16 November 2014.
^ Wessels, Duane (2004). Squid The Definitive Guide. O’Reilly. pp. 130. ISBN 978-0-596-00162-9.
^ Marshall, James. “CGIProxy”. Retrieved 12 November 2018.
^ “The Limit
What is a Proxy Server? How It Works & How to Use It | Fortinet
What Is a Proxy Server?
A proxy server provides a gateway between users and the internet. It is a server, referred to as an “intermediary” because it goes between end-users and the web pages they visit online.
When a computer connects to the internet, it uses an IP address. This is similar to your home’s street address, telling incoming data where to go and marking outgoing data with a return address for other devices to authenticate. A proxy server is essentially a computer on the internet that has an IP address of its own.
Proxy Servers and Network Security
Proxies provide a valuable layer of security for your computer. They can be set up as web filters or firewalls, protecting your computer from internet threats like malware.
This extra security is also valuable when coupled with a secure web gateway or other email security products. This way, you can filter traffic according to its level of safety or how much traffic your network—or individual computers—can handle.
How to use a proxy? Some people use proxies for personal purposes, such as hiding their location while watching movies online, for example. For a company, however, they can be used to accomplish several key tasks such as:
Improve security
Secure employees’ internet activity from people trying to snoop on them
Balance internet traffic to prevent crashes
Control the websites employees and staff access in the office
Save bandwidth by caching files or compressing incoming traffic
How a Proxy Works
Because a proxy server has its own IP address, it acts as a go-between for a computer and the internet. Your computer knows this address, and when you send a request on the internet, it is routed to the proxy, which then gets the response from the web server and forwards the data from the page to your computer’s browser, like Chrome, Safari, Firefox, or Microsoft Edge
How to Get a Proxy
There are hardware and software versions. Hardware connections sit between your network and the internet, where they get, send, and forward data from the web. Software proxies are typically hosted by a provider or reside in the cloud. You download and install an application on your computer that facilitates interaction with the proxy.
Often, a software proxy can be obtained for a monthly fee. Sometimes, they are free. The free versions tend to offer users fewer addresses and may only cover a few devices, while the paid proxies can meet the demands of a business with many devices.
How Is the Server Set Up?
To get started with a proxy server, you have to configure it in your computer, device, or network. Each operating system has its own setup procedures, so check the steps required for your computer or network.
In most cases, however, setup means using an automatic configuration script. If you want to do it manually, there will be options to enter the IP address and the appropriate port.
How Does the Proxy Protect Computer Privacy and Data?
A proxy server performs the function of a firewall and filter. The end-user or a network administrator can choose a proxy designed to protect data and privacy. This examines the data going in and out of your computer or network. It then applies rules to prevent you from having to expose your digital address to the world. Only the proxy’s IP address is seen by hackers or other bad actors. Without your personal IP address, people on the internet do not have direct access to your personal data, schedules, apps, or files.
With it in place, web requests go to the proxy, which then reaches out and gets what you want from the internet. If the server has encryption capabilities, passwords and other personal data get an extra tier of protection.
Benefits of a Proxy Server
Proxies come with several benefits that can give your business an advantage:
Enhanced security: Can act like a firewall between your systems and the internet. Without them, hackers have easy access to your IP address, which they can use to infiltrate your computer or network.
Private browsing, watching, listening, and shopping: Use different proxies to help you avoid getting inundated with unwanted ads or the collection of IP-specific data.
Access to location-specific content: You can designate a proxy server with an address associated with another country. You can, in effect, make it look like you are in that country and gain full access to all the content computers in that country are allowed to interact with.
Prevent employees from browsing inappropriate or distracting sites: You can use it to block access to websites that run contrary to your organization’s principles. Also, you can block sites that typically end up distracting employees from important tasks. Some organizations block social media sites like Facebook and others to remove time-wasting temptations.
Types of Proxy Servers
While all proxy servers give users an alternate address with which to use the internet, there are several different kinds—each with its own features.
Forward Proxy
A forward proxy sits in front of clients and is used to get data to groups of users within an internal network. When a request is sent, the proxy server examines it to decide whether it should proceed with making a connection.
A forward proxy is best suited for internal networks that need a single point of entry. It provides IP address security for those in the network and allows for straightforward administrative control. However, a forward proxy may limit an organization’s ability to cater to the needs of individual end-users.
Transparent Proxy
A transparent proxy can give users an experience identical to what they would have if they were using their home computer. In that way, it is “transparent. ” They can also be “forced” on users, meaning they are connected without knowing it.
Transparent proxies are well-suited for companies that want to make use of a proxy without making employees aware they are using one. It carries the advantage of providing a seamless user experience. On the other hand, transparent proxies are more susceptible to certain security threats, such as SYN-flood denial-of-service attacks.
Anonymous Proxy
An anonymous proxy focuses on making internet activity untraceable. It works by accessing the internet on behalf of the user while hiding their identity and computer information.
A transparent proxy is best suited for users who want to have full anonymity while accessing the internet. While transparent proxies provide some of the best identity protection possible, they are not without drawbacks. Many view the use of transparent proxies as underhanded, and users sometimes face pushback or discrimination as a result.
High Anonymity Proxy
A high anonymity proxy is an anonymous proxy that takes anonymity one step further. It works by erasing your information before the proxy attempts to connect to the target site.
The server is best suited for users for whom anonymity is an absolute necessity, such as employees who do not want their activity traced back to the organization. On the downside, some of them, particularly the free ones, are decoys set up to trap users in order to access their personal information or data.
Distorting Proxy
A distorting proxy identifies itself as a proxy to a website but hides its own identity. It does this by changing its IP address to an incorrect one.
Distorting proxies are a good choice for people who want to hide their location while accessing the internet. This type of proxy can make it look like you are browsing from a specific country and give you the advantage of hiding not just your identity but that of the proxy, too. This means even if you are associated with the proxy, your identity is still secure. However, some websites automatically block distorting proxies, which could keep an end-user from accessing sites they need.
Data Center Proxy
Data center proxies are not affiliated with an internet service provider (ISP) but are provided by another corporation through a data center. The proxy server exists in a physical data center, and the user’s requests are routed through that server.
Data center proxies are a good choice for people who need quick response times and an inexpensive solution. They are therefore a good choice for people who need to gather intelligence on a person or organization very quickly. They carry the benefit of giving users the power to swiftly and inexpensively harvest data. On the other hand, they do not offer the highest level of anonymity, which may put users’ information or identity at risk.
Residential Proxy
A residential proxy gives you an IP address that belongs to a specific, physical device. All requests are then channeled through that device.
Residential proxies are well-suited for users who need to verify the ads that go on their website, so you can block cookies, suspicious or unwanted ads from competitors or bad actors. Residential proxies are more trustworthy than other proxy options. However, they often cost more money to use, so users should carefully analyze whether the benefits are worth the extra investment.
Public Proxy
A public proxy is accessible by anyone free of charge. It works by giving users access to its IP address, hiding their identity as they visit sites.
Public proxies are best suited for users for whom cost is a major concern and security and speed are not. Although they are free and easily accessible, they are often slow because they get bogged down with free users. When you use a public proxy, you also run an increased risk of having your information accessed by others on the internet.
Shared Proxy
Shared proxies are used by more than one user at once. They give you access to an IP address that may be shared by other people, and then you can surf the internet while appearing to browse from a location of your choice.
Shared proxies are a solid option for people who do not have a lot of money to spend and do not necessarily need a fast connection. The main advantage of a shared proxy is its low cost. Because they are shared by others, you may get blamed for someone else’s bad decisions, which could get you banned from a site.
SSL Proxy
A secure sockets layer (SSL) proxy provides decryption between the client and the server. As the data is encrypted in both directions, the proxy hides its existence from both the client and the server.
These proxies are best suited for organizations that need enhanced protection against threats that the SSL protocol reveals and stops. Because Google prefers servers that use SSL, an SSL proxy, when used in connection with a website, may help its search engine ranking. On the downside, content encrypted on an SSL proxy cannot be cached, so when visiting websites multiple times, you may experience slower performance than you would otherwise.
Rotating Proxy
A rotating proxy assigns a different IP address to each user that connects to it. As users connect, they are given an address that is unique from the device that connected before it.
Rotating proxies are ideal for users who need to do a lot of high-volume, continuous web scraping. They allow you to return to the same website again and again anonymously. However, you have to be careful when choosing rotating proxy services. Some of them contain public or shared proxies that could expose your data.
Reverse Proxy
Unlike a forward proxy, which sits in front of clients, a reverse proxy is positioned in front of web servers and forwards requests from a browser to the web servers. It works by intercepting requests from the user at the network edge of the web server. It then sends the requests to and receives replies from the origin server.
Reverse proxies are a strong option for popular websites that need to balance the load of many incoming requests. They can help an organization reduce bandwidth load because they act like another web server managing incoming requests. The downside is reverse proxies can potentially expose the HTTP server architecture if an attacker is able to penetrate it. This means network administrators may have to beef up or reposition their firewall if they are using a reverse proxy.
Proxy Server vs. VPN
On the surface, proxy servers and virtual private networks (VPNs) may seem interchangeable because they both route requests and responses through an external server. Both also allow you to access websites that would otherwise block the country you’re physically located in. However, VPNs provide better protection against hackers because they encrypt all traffic.
Choosing VPN or Proxy
If you need to constantly access the internet to send and receive data that should be encrypted or if your company has to reveal data you must hide from hackers and corporate spies, a VPN would be a better choice.
If an organization merely needs to allow its users to browse the internet anonymously, a proxy server may do the trick. This is the better solution if you simply want to know which websites team members are using or you want to make sure they have access to sites that block users from your country.
A VPN is better suited for business use because users usually need secure data transmission in both directions. Company information and personnel data can be very valuable in the wrong hands, and a VPN provides the encryption you need to keep it protected. For personal use where a breach would only affect you, a single user, a proxy server may be an adequate choice. You can also use both technologies simultaneously, particularly if you want to limit the websites that users within your network visit while also encrypting their communications.
How Fortinet Can Help
FortiGate has the capability of both proxies and VPNs. It shields users from data breaches that often happen with high-speed traffic and uses IPsec and SSL to enhance security. FortiGate also harnesses the power of the FortiASIC hardware accelerator to enhance performance without compromising privacy. Secure your network with FortiGate VPN and proxy capabilities. Contact us to learn more.
Frequently Asked Questions about proxy serveris
What is proxy authentication?
Proxy Authentication enables you to configure the authentication method used by the proxy. This determines how client machines are validated when accessing the Internet. … This method is more secure since unlike Basic Authentication it does not transmit user credentials over the network.
What is a proxy firewall?
A proxy firewall is the most secure form of firewall, which filters messages at the application layer to protect network resources. … A proxy server addresses this gap by providing a gateway or intermediary between computers and servers on the internet to secure data that goes in and out of a network.
What is a proxy request?
A proxy server is an application or system that acts as an intermediary between your computer and the internet, or more specifically, the client and server. The proxy makes requests on your behalf to websites, servers, and other internet services.
