New worm targets Sasser code flaw

IDG News Service - A new Internet worm is spreading by exploiting a flaw in the Sasser worm, according to an alert issued yesterday.
The new worm, tentatively named Dabber, takes advantage of a vulnerability in an FTP server component in the Sasser worm and may have infected thousands of computers already infected with Sasser. Dabber is believed to be the first worm that spreads by specifically targeting a flaw in another worm's code, according to an advisory published by LURHQ Corp., a Chicago managed security services company.
Using code written to exploit the FTP flaw, the recently released worm scans the Internet for Port 5554 to identify computers running Microsoft Corp.'s Windows operating system that are infected with Sasser, LURHQ said.
When it finds vulnerable hosts, it connects to the victim and uses a built-in FTP server to transfer the worm file, named package.exe, to the system. When it runs, the Dabber worm installs itself on Windows and then shuts down the Sasser worm and other worm processes, preventing them from running again. Dabber also opens TCP Port 9898 as a back door, which can be used by a remote attacker to download other code or communicate with the infected host, LURHQ said.
As of yesterday, Dabber didn't appear to be spreading quickly, but the number of infections was escalating, LURHQ said.
Sasser, which appeared on May 1 (see story), exploits a recently disclosed hole in a Windows component called the Local Security Authority Subsystem Service, or LSASS. Microsoft released a software patch, MS04-011, on April 13.
Dabber is similar to Sasser and earlier worms like Blaster because users don't need to receive an e-mail message or open a file to be infected. Instead, just having a Sasser-infected Windows machine connected to the Internet is enough to catch Dabber.
Last week, Microsoft acknowledged that more than 1.5 million copies of a Sasser cleanup tool were downloaded from its Web site within the first 48 hours after it was offered.
In its advisory, LURHQ posted instructions for shutting down and removing Dabber.