FAQ: Everything you need to know to protect your systems from the Storm Worm

Computerworld - What is the Storm Worm?
Not really a worm (it's actually a Trojan-bearing e-mail), but it's certainly a storm. Spotted in the wild on Jan. 17, the executable file reportedly infected more than 300,000 PCs within a week. That rate of infection would make this the worst outbreak since Sober.O back in spring 2005.

What are other companies calling it?
F-Secure first identified the worm and called it the Storm Worm, based on its original subject line. Several aliases for the Trojan have been identified and grouped as Small.DAM. Other nomenclatures:

FrSIRT -- Downloader-BAI!M711 (via McAfee)
McAfee -- Downloader-BAI
Sophos -- Troj/Dorf-Fam
Symantec -- Trojan.Peacomm
Trend Micro -- TROJ_SMALL.EDW or CME-711
Windows Live OneCare -- Win32/Nuwar.N@MM!CME-711

Which platforms are susceptible?
Windows 95 and later, including Windows NT and Windows Server 2003. No Vista infections have been reported as of Jan. 23.

How does it infect?
Mainly via spam, though it has been dropped on systems by other malware -- particularly WORM.NUWAR.CQ, a.k.a. W32/Nuwar@MM. That downloader has been used recently to drop other malware, particularly downloader-ARL.

What subject lines should I be watching for with that spam?
They're changing rapidly to fit the latest headlines -- that's one of the things that makes this infection interesting.

The first subject lines concerned weather events in Europe -- hence the name. More recent subject lines mention severe U.S. weather, Chinese missiles, Russian missiles, Saddam Hussein (alive in some Elvis-like fashion), a purported terrorist attack on the Supreme Court and/or Congress, a paroled murderer in Michigan, and the always popular naked marauding teenagers.

Some quarters have reported finding the Trojan in romance-themed messages, presumably to take advantage of the Valentine's Day rush. An earlier infection dropped by the Nuwar downloader carried New Year's greetings, and the .exe claimed to be a greeting card or postcard. A reader of F-Secure's "News from the Lab" blog points out that the latest list of subjects bears a resemblance to a list of cards in the romance category at 2000greetings.com, indicating that the perpetrators may be casting their nets even wider for "inspiration."

What's the payload?
The message (in the case of spam) is accompanied by a compressed .exe file of about 29KB. The name of that file also varies, though not as much as the subject lines: Full Clip.exe, Full Story.exe, Video.exe, Read More.exe and other variations have been spotted.

If the user clicks on the file, a few things happen. The program installs two .ini files, peers.ini and wincom32.ini, and a system file called wincom32.sys. That's the Trojan, and it has rootkit capabilities (enabling the infection to disguise itself and its processes) to boot.

Once installed, the Trojan reaches out to a number of other machines, looking to download five files: TROJ_AGENT.JVH, TROJ_AGENT.JVI, TROJ_AGENT.JVJ, TROJ_DORF.AA, and WORM_NUWAR.CQ. (Note that, as mentioned above, Nuwar has been spotted as an infection vector for the Trojan itself.) It also opens up a slew of UDP ports, looking to make covert peer-to-peer-style connections to various IP addresses.