Anonymity on the Internet
Even though anonymity and pseudonymity is not something new with the Internet, the net has increased the ease for a person to distribute anonymous and pseudonymous messages. Anonymity on the Internet is almost never 100 %, there is always a possibility to find the perpetrator, especially if the same person uses the same way to gain anonymity multiple times. 6
The security for the anonymous user is not very high in this case. The IP number (physical address) of the computer used is usually logged, often also the host name (logical name). Many people connect to the Internet using a temporary IP number assigned to them for a single session. But also such numbers are logged by the ISP (Internet Service Provider) and it is possible to find out who used a certain IP number at a certain time, provided that the ISP assists in the identification. There are also other well-known methods for breaking anonymity, for example elements can be included on a web page, which communicates information without knowledge of the person watching the web page. Some ISPs have a policy of always assisting such searches for the anonymous users. In this way they avoid tricky decisions on when to assist and not assist such searches.
In the case of e-mail, the e-mail header itself contains a trace of the route of a message. This trace is not normally shown to recipients, but most mailers have a command named something like full headers to show this information. …(example omitted)
To gain higher protection of anonymity, a clever impostor can use various techniques to make identification more difficult. Examples of such techniques are:
IP numbers, trace lists and other identification can be falsified. Since this information is often created in servers, it is easier to falsify them if you have control of one or more servers.
Communication is done in several steps. The impostor first connects to computer A, then from this computer to computer B, then from this to computer C, etc. To find the real person, all the steps must be followed backward. The trace needs transaction logs, and such logs are not always produced automatically. Logging may have to be switched on. So by co-operating with the owner of computer C, it is possible to switch on logging so that the next time the impostor appears, he is traced back to computer B. In the next step, the owner of computer B is asked to help trace the impostor further. Thus, through a tedious process, including the co-operation of all the used computers in the chain, the real person can be found. A famous example is described in the book [Stoll 1989], which describes the tracing of a hacker which used a series of servers, without permission, to conceal the route from the user to the final anonymous activity.
Anonymity servers
Since anonymity has positive uses (see above) there are people who run anonymity servers. An anonymity server receives messages, and resends them under another identity. There are two types of anonymity servers:
Full anonymity servers, where no identifying information is forwarded.
Pseudonymous servers, where the message is forwarded under a pseudonym. The server stores the real name behind a pseudonym, and can receive replies sent to the pseudonym, and transmit them back to the originator. 7
There are companies which market anonymity servers and there is a research area on improving the techniques of such software [McCullagh 2001].
People who want to achieve high security against being revealed, often use several anonymity servers in sequence. …