Hackers have programmed a Trojan that uses Google Groups newsgroups to distribute commands.
Trojan distribution via newsgroups has existed for more than a decade, but using newsgroups as a command and control channel is a new innovation.
The
Grups Trojan itself is quite simple and is only noteworthy for the command and control structure it deploys. The malware is programmed to log into a Chinese language newsgroup to receive commands, Symantec security researcher Gavin O'Gorman
writes.
When successfully logged in, the Trojan requests a page from a private newsgroup, escape2sun. The page contains commands for the Trojan to carry out. The command consists of an index number, a command line to execute, and optionally, a file to download. Responses are uploaded as posts to the newsgroup using the index number as a subject.
The post and page contents are encrypted using the RC4 stream cipher and then base64 encoded. The attacker can thus issue confidential commands and read responses. If no command is received from the static page, the infected host uploads the current time.
