An anonymizer or an anonymous proxy is a tool that attempts to make activity on the Internet untraceable.[1] It accesses the Internet on the user's behalf, protecting personal information by hiding the source computer's identifying information.[2]
Purposes
There are many purposes for using anonymizers. Anonymizers help minimize risk. They can be used to expose human rights abuses without retribution, to speak about a taboo without loss of reputation, to receive information within a repressive regime, to prevent identity theft, or to protect search histories from public disclosure.
Anonymizers can be used by individuals wishing to avoid the consequences of engaging in criminal, disruptive, or socially unacceptable behaviour online. Also, they are used to bypass web technologies that limit online content access to a certain number of minutes or quantity of data.
Risks and security
Anonymizers are not entirely secure. If an anonymizer keeps logs of incoming and outgoing connections and the anonymizer is physically located in a country where it is subjected to warrant searches then there is a potential risk that government officials can reverse engineer and identify all users who used the anonymizer and how they used it. Most anonymizers state they do not keep logs but there is currently no way to confirm that. However, if the user used another anonymizer to connect to the exposed anonymizer, that user is still anonymous. This is sometimes called daisy-chaining.
Further, an untrustworthy web based anonymizer is capable of man in the middle attacks. The anonymizer can read, inject, and modify content into the message that the user is sending as well as receiving. The anonymizer can intercept and record private unencrypted information such as username and password credentials, credit card numbers, e-mails, etc. that have been transported using the anonymizer. To avoid this, content should be encrypted and credentials should be exchanged outside of the anonymizer.
For even trustworthy anonymizers, anonymizers cannot filter out any malicious code that may reveal the identity of the user who wishes to remain anonymous. See malware. Care should be taken to prevent information leaks. For example, anonymizing an HTTP connection but not a DNS lookup can reveal the location of the viewer.
Anonymizers also present a high value target. Groups opposite the people who want to remain anonymous target public anonymizers, especially as they are often misused.[3]
Free anonymizers, mainly open socks and http proxies, are usually operated against the knowledge of the server owner, botnetworks and other malware are known to install such services. They are used to log passwords or place advertisements/malware into the (http/email)traffic and cause high damages to the server owner because of the high bandwidth consumed and the security breach. "Bad" HTTP proxies almost always anonymize the connection by hiding the real identity of the client user to be more attractive, this can be detected through a free proxy analyzer.[4]
Use of anonymizers
Protocol specific anonymizers
Sometimes anonymizers are implemented to work only with one particular protocol. The advantage is that no extra software is needed. The operation occurs in this manner: A connection is made by the user to the anonymizer. Commands to the anonymizer are included inside a typical message. The anonymizer then makes a connection to the resource specified by the in-band command and relays the message with the command stripped out.
An example of a protocol specific anonymizer is an anonymous remailer for e-mail. Also of note are web proxies and bouncers for FTP and IRC.
Protocol independent anonymizers
Protocol independence can be achieved by creating a tunnel to an anonymizer. The technology to do so varies. Protocols used by anonymizer services may include SOCKS, PPTP, or OpenVPN.
In this case either the desired application must support the tunneling protocol, or a piece of software must be installed to force all connections through the tunnel. Web browsers, FTP and IRC clients often support SOCKS for example, unlike telnet.
Use of multiple relays
One example of "daisy-chained" anonymizing proxies is the "Tor network". Tor does not encrypt your traffic[5] from end to end, it builds up a series of encrypted connections through the relays in the TOR network. An additional layer of encryption should be used with Tor if end-to-end encryption is required. See risks of using anonymous proxy servers.
Another example of multiple relays is sending an e-mail to an anonymizing remailer, which relays it to another remailer, which eventually relays it to its destination.
See also
References
