The Penet remailer (anon.penet.fi) was a pseudonymous remailer operated by Johan "Julf" Helsingius of Finland from 1993 to 1996. Its initial creation stemmed from an argument in a Finnish newsgroup over whether people should be required to tie their real name to their online communications. Julf believed that people should not—indeed, could not—be required to do so. In his own words:
"Some people from a university network really argued about if everybody should put their proper name on the messages and everybody should be accountable, so you could actually verify that it is the person who is sending the messages. And I kept arguing that the Internet just doesn't work that way, and if somebody actually tries to enforce that, the Internet will always find a solution around it. And just to prove my point, I spent two days or something cooking up the first version of the server, just to prove a point."
Implementation
Julf's remailer worked by receiving an e-mail from a person, stripping away all the technical information that could be used to identify the original source of the e-mail, and then remailing the message to its final destination. The result provided Internet users with the ability to send e-mail messages and post to Usenet newsgroups without revealing their identities. In addition, the Penet remailer used a type of “post office box” system in which users could claim their own anonymous e-mail addresses of the form anxxxxx@anon.penet.fi, allowing them to assign pseudonymous identities to their anonymous messages, and to receive messages sent to their (anonymous) e-mail addresses. While the basic concept was effective, the Penet remailer had several vulnerabilities which threatened the anonymity of its users. Chief among them was the need to store a list of real e-mail addresses mapped to the corresponding anonymous e-mail addresses on the server. A potential attacker needed only to access that list to compromise the identities of all of Penet's users. The Penet remailer was on two occasions required by the legal system in Finland (the country where the Penet server hardware resided) to turn over the real e-mail address that was mapped to an anonymous e-mail address. Another potential vulnerability was that messages sent to and from the remailer were all sent in cleartext, making it vulnerable to electronic eavesdropping. Later anonymous remailer designs, such as the Cypherpunk and Mixmaster designs, adopted more sophisticated techniques to try to overcome these vulnerabilities, including the use of encryption to prevent eavesdropping, and also the technique known as onion routing to allow the existence of pseudonymous remailers in which no record of a user's real e-mail address is stored by the remailer. Despite its relatively weak security, the Penet remailer was a hugely popular remailer owing to its ease of anonymous account set-up and use compared to more secure but less user-friendly remailers, and had over 700,000 registered users at the time of its shutdown in September 1996.
First compromise In the summer of 1994, word spread online of the Penet remailer being compromised, with the announcement being made at the hacker convention DEF CON II. Wired magazine reported at the time:
An official announcement was made at this year's DefCon II that anon.penet.fi has been seriously compromised. We strongly suggest that you not trust this anonymous remailer. (Word has it that some folks are working on a PGP-based service.) We'll keep you posted. This was followed a year later by a mention in the announcement for DEF CON III:
SPEAKERS Sarah Gordon, AKA Theora, a veteran of DC II will be presenting another speech this year. Last year she organized a round table discussion with Phil Zimmermann and Presence, and revealed that the Anonymous remailer anon.penet.fi was compromised. TOPIC: Not Announced Yet.
Second compromise The second reported compromise of the Penet remailer occurred in February 1995 at the behest of the Church of Scientology. Claiming that a file had been stolen from one of the Church's internal computer servers and posted to the newsgroup alt.religion.scientology by a Penet user, representatives of the Church contacted Interpol, who in turn contacted the Finnish police, who issued a search warrant demanding that Julf hand over data on the users of the Penet remailer. Initially Julf was asked to turn over the identities of all users of his remailer (which numbered 200,000 at the time), but he managed a compromise and revealed only the single user being sought by the Church of Scientology. The anonymous user in question used the handle "-AB-" when posting anonymously, and their real e-mail address indicated that they were an alumnus or alumna of the California Institute of Technology. The document he posted was an internal report by a Scientology private investigator, Eugene Ingram, about an incident that had occurred involving a man named Tom Klemesrud, a BBS operator involved in a controversy. The confusing story became known on the Internet as the "Miss Blood Incident". Eventually the Church learned the real identity of "-AB-" to be Tom Rummelhart, a Scientologist and computer operator responsible for some of the maintenance of the Church of Scientology's INCOMM computer system. The fate of "-AB-" after the Church of Scientology learned his true identity is unknown. Years later in 2003, a two-part story entitled "What Really Happened in INCOMM - Part 1" and "What Really Happened in INCOMM – Part 2" was posted to alt.religion.scientology by a former Scientologist named Dan Garvin, which described events within the Church leading up to and stemming from the Penet posting by "-AB-".
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