The Benjamin worm uses KaZaa Peer-To-Peer (P2P) network to spread. The KaZaa network allows its participants to exchange files with each other, using the special client software. The worm opens benjamin.xww.de Web-site to view an advertisement. The worm is written in Borland Delphi and is about 216 kilobytes long. The worm's file is compressed with ASPack file compressor. Besides the worm uses a decoy - it appends random data to its end that increases its size 2-3 times.
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When the worm's file is started, it shows a fake error message: Error Access error #03A:94574: Invalid pointer operation File possibly corrupted. Then it copies itself into Windows System directory as EXPLORER.SCR and creates two keys in the System Registry:
This way, the worm makes sure that it is always executed when Windows starts.
The worm spreads only from and to computers where KaZaa network clients are installed. The worm reads the settings of the KaZaa client from the System Registry, creates the directory named \Sys32\ in Windows Temp folder and makes this directory visible to all clients of Kazaa network. The worm then fills this directory with its copies with various names which are taken from the list inside the worm's body. The list contains numerous titles of popular software, movies, games and music, and some commonly used search words. For example, this is only the part of the list with titles starting with 'A' letter:
The worm spreads in the following way: a KaZaa network user searches for any file (for example the file that has the 'game' string in its file name) in the KaZaa network and finds it on the list of accessible files from an infected computer. The user downloads this file and starts it, thus infecting his own machine.
F-Secure Anti-Virus detects Benjamin worm with the updates published in May 20th, 2002: