An open proxy is a type of

proxy server 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. Instead of connecting directly to a server that can fulfill a reques ...

that is accessible by any

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, p ...

user. Generally, a proxy server only allows users ''within a network group'' (i.e. a closed proxy) to

store and forward Store and forward is a telecommunications technique in which information is sent to an intermediate station where it is kept and sent at a later time to the final destination or to another intermediate station. The intermediate station, or node in ...

Internet services such as DNS or web pages to reduce and control the

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

used by the group. With an ''open'' proxy, however, any user on the Internet is able to use this forwarding service. Open proxy h2g2bob

Advantages

An ''anonymous open proxy'' is useful to those looking for online anonymity and privacy, as it can help users hide their

IP address An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...

from web servers since the server requests appear to originate from the proxy server. It makes it harder to reveal their identity and thereby helps preserve their perceived security while browsing

the web The World Wide Web (WWW), commonly known as the Web, is an information system enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through we ...

or using other

internet service An Internet service provider (ISP) is an organization that provides services for accessing, using, or participating in the Internet. ISPs can be organized in various forms, such as commercial, community-owned, non-profit, or otherwise privat ...

s. Real anonymity and extensive

internet security Internet security is a branch of computer security. It encompasses the Internet, browser security, web site security, and network security as it applies to other applications or operating systems as a whole. Its objective is to establish rules ...

might not be achieved by this measure alone as website operators can use client-side scripts to determine the browser's real IP address and the open proxy may be keeping logs of all connections. Open proxies also don't stop

tracking cookies HTTP cookies (also called web cookies, Internet cookies, browser cookies, or simply cookies) are small blocks of data created by a web server while a user is browsing a website and placed on the user's computer or other device by the user's we ...

and fingerprinters from identifying users. Most public

VPN A virtual private network (VPN) extends a private network across a public network and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. The be ...

s work through open proxies.

Disadvantages

It is possible for a computer to run as an open proxy server without the computer's owner knowing it. This can result from misconfiguration of proxy software running on the computer, or from infection with

malware Malware (a portmanteau for ''malicious software'') is any software intentionally designed to cause disruption to a computer, server, client, or computer network, leak private information, gain unauthorized access to information or systems, depr ...

(

viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's ...

trojans Trojan or Trojans may refer to: * Of or from the ancient city of Troy * Trojan language, the language of the historical Trojans Arts and entertainment Music * ''Les Troyens'' ('The Trojans'), an opera by Berlioz, premiered part 1863, part 189 ...

worms Worms may refer to: *Worm, an invertebrate animal with a tube-like body and no limbs Places *Worms, Germany Worms () is a city in Rhineland-Palatinate, Germany, situated on the Upper Rhine about south-southwest of Frankfurt am Main. It had ...

) designed for this purpose. If it is caused by malware, the infected computer is known as a

zombie computer In computing, a zombie is a computer connected to the Internet that has been compromised by a hacker via a computer virus, computer worm, or trojan horse program and can be used to perform malicious tasks under the remote direction of the hac ...

Testing for access from an open proxy

Because open proxies are often implicated in abuse, a number of methods have been developed to detect them and to refuse service to them.

IRC Internet Relay Chat (IRC) is a text-based chat system for instant messaging. IRC is designed for group communication in discussion forums, called '' channels'', but also allows one-on-one communication via private messages as well as chat an ...

networks with strict usage policies automatically test client systems for known types of open proxies. Likewise, a

mail server Within the Internet email system, a message transfer agent (MTA), or mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using SMTP. The terms mail server, mail exchanger, and MX ho ...

may be configured to automatically test mail senders for open proxies, using

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consist ...

such as proxycheck. Groups of IRC and electronic mail operators run

DNSBL A Domain Name System blocklist, Domain Name System-based blackhole list, Domain Name System blacklist (DNSBL) or real-time blackhole list (RBL) is a service for operation of mail servers to perform a check via a Domain Name System (DNS) query whe ...

s publishing lists of the

es of known open proxies, such as

AHBL The Abusive Hosts Blocking List (AHBL) was an internet abuse tracking and filtering system developed by The Summit Open Source Development Group, and based on the original Summit Blocking List (2000–2002). Its DNSBLs were shut down on Jan 1, ...

, CBL,

NJABL Not Just Another Bogus List (NJABL) was a DNS blacklist. NJABL maintained a list of known and potential spam sources (open mail relays, open proxies, open form to mail HTTP gateways, dynamic IP pools, and direct spammers) for the purpose of being ...

(till 2013), and

SORBS Sorbs ( hsb, Serbja, dsb, Serby, german: Sorben; also known as Lusatians, Lusatian Serbs and Wends) are a indigenous West Slavic ethnic group predominantly inhabiting the parts of Lusatia located in the German states of Saxony and Branden ...

(in operation since 2002). The AHBL discontinued public access in 2015.

References

{{Reflist Internet security Proxy servers es:Proxy#Proxy Abierto pt:Proxy#Proxy abreto

Advantages

Disadvantages

Testing for access from an open proxy

See also

References