The Bagle virus saga takes a new twist today with four new members of the worm family. Bagle-Q and its three new siblings use an unusual method of infection in an attempt to bypass AV protection at email gateways. Each of the four viruses infect only Windows PCs. Bagle-Q is the more widely spread of the four.
Unlike most email viruses, the four new Bagle worms do not carry email attachments, making them much more difficult to spot. If a user opens the message - and their machine has not been patched against a five-month old critical vulnerability - malicious code is automatically downloaded from the PC which sent the "carrier" email.
Once installed, the malicious code is programmed to deactivate a wide range of security applications, potentially opening up victims' PCc to more virus or hacker attacks. Bagle-Q and Bagle-R also attempt to spread by file-sharing networks.
Carole Theriault, a security consultant at AV firm Sophos, told El Reg that the infection mode of Bagle-Q will surprise people who think they can only get infected by clicking on an attachment.
Bagle-Q and Bagle-R have spread fairly extensively through Asia (particularly Korea) and Australia overnight. US and European users are urged to take action to halt the worms' spread. There are fewer reports concerned Bagle-S and Bagle-T.
Users are once again urged to update their AV software against the latest threat. Businesses can also protect themselves at their gateway firewall, preventing computers on their network from downloading the worm from outside.
Thomas Kristensen, CTO of security tracking outfit Secunia, said that Bagle-Q is more advanced than earlier versions in its propagation technique. Bagle-Q exploits an Object Data vulnerability in Internet Explorer, which allows it to be executed automatically on an un-patched system.
From the start, Secunia considered the Object Data vulnerability as far more serious than most, going as far as making an online test available for people to check if they are at risk.
Microsoft first tried to patch the vulnerability in August.
However, this proved inefficient, and a fully-working fix was released in October.
A patch for the Microsoft security vulnerability exploited by Bagle-Q and R can be found here (this is a cumulative fix designed to repair other flaws too). This might also be a good time to apply other MS patches (complete list here).
Worm War Three
The unknown author(s) of Bagle have used progressively more sophisticated tricks to bypass AV protection. After first burying malicious code in encrypted archive files, variants are now exploiting Microsoft vulnerabilities to travel across the Net on auto-pilot.
After conducting a war of words with the group behind the NetSky worm, Bagle’s creators are now directing their fire against security firms and end users. The bad guys are running the show and appear to have the upper hand. ®