Risk: Medium
Virus writers are distributing viral source code with the latest version of the Bagle virus series, Bagle-AD. Much like its 29 predecessors, Bagle-AD is a mass-mailing worm that is packed using UPX file compression. It comes in the form of a password-protected .ZIP file, with the password included in the message body as plain text or within an image. The ZIP file contains an executable with the extensions EXE, COM or SCR.
After being executed, Bagle-AD emails itself, using its own built-in SMTP engine, to addresses harvested from an infected PC. Infected emails come from spoofed email addresses. The remote access component of the virus listens to TCP port 1234 for commands, a feature which allows crackers to use infected PCs as zombie drones in DDoS attack networks or to distribute spam.
When mass-mailing itself, the worm may also include a copy of its source code (written in Assembler) within a ZIP archive. This makes it easier for copycats to design more versions of the virus. It also gives its author an excuse for why source code is discovered on a PC, if he is ever arrested.
Anti-virus firm McAfee increased the risk assessment on Bagle-AD, reclassifying the worm as a medium-risk threat. Bagle-AD is a Windows-only menace.