New Trojan Targets Windows SystemsNew Trojan Targets Windows Systems

Computer-security companies warned Wednesday that a new malicious Trojan horse that targets Windows systems has been spotted on the Internet. Dubbed Phatbot, the Trojan was first noticed by antivirus companies earlier this week.

"We started getting reports of infections early Monday," says Craig Schmugar, a virus researcher with McAfee antivirus and vulnerability emergency-response team at Network Associates Inc.

Phatbot, which already has several variants, is leveraging a long list of software flaws to infect systems. According to security researchers, Phatbot scans for systems that have unpatched Windows vulnerabilities, including DCOM, DCOM2, locator service, network shares using weak passwords, WebDav, and the Windows Workstation Service. It will also attack systems already infected with the MyDoom worm.

Some variants of Phatbot can be controlled by attackers through Internet Relay Chat, while others can be controlled through peer-to-peer file-sharing technology.

Once the Trojan infects a system, it can try to use that system to send spam; steal Microsoft Windows Product Keys; kill previous infections of Blaster, Welchia, and Sobig.F worms; and steal Internet Relay Chat or IRC operator logon information and user names and passwords from FTP network traffic. It also can shut down common antivirus applications and block access to many antivirus vendor Web sites, Schmugar says. He says the majority of infections have so far occurred in Asia, with some in the United States.

Security vendor iDefense Inc. has spotted successful Phatbot infections, but Ken Dunham, director of malicious code, says it isn't the number of infected machines that's worrisome but the networks that are placed at risk with infected systems. "Large networks are clearly the target of this attack, as well as opportunistically attacking home users," he says.

Joe Stewart, senior security researcher at managed security services firm Lurhq Corp., says that while monitoring Phatbot he witnessed at least 1,000 infected systems in about an hour.

Because Phatbot doesn't cause an immediate and obvious problem, systems could remain infected for some time before users realize they have it. Most antivirus vendors have updated their antivirus signature files to spot Phatbot or soon will.