More than 100 Web servers are still distributing the "Scob" malicious code, first identified two weeks ago as code used in a widespread attack to plant Trojan horse programs on vulnerable computers, according to one computer security company. That attack used compromised Microsoft Internet Information Services Web servers to distribute the Trojan horse programs.

Enterprise security software maker Websense discovered 114 Web sites that are distributing variations of a malicious JavaScript program known as "Scob," or "Download.Ject." Whereas the attack initially targeted only Web servers running IIS Version 5, the majority of infected sites now run IIS Version 6, after administrators upgraded the systems, unaware their servers were already infected, said Dan Hubbard, director of security and technology research at Websense.

Websense, of San Diego, discovered the infected sites during its daily "mining" of more than 24 million Web sites, which the company uses to detect Web- and Internet-based threats. The company modified its mining algorithms on June 24 to search for Web sites distributing the Scob code, and has been monitoring such sites since then, he said.

The 100 affected sites are all running either IIS 5.0 or 6.0. Attack code distributed by the infected servers still points to Web sites used in the attack, which were taken off-line shortly after news of the original attacks spread, meaning that the continued malicious code attacks have probably not resulted in new Trojan infections, Hubbard said.

First detected on June 24, the Scob attacks have been attributed to a Russian hacking group known as the "hangUP team," which used a recently-patched buffer overflow vulnerability in Microsoft's implementation of SSL (secure sockets layer) to compromise vulnerable Windows 2000 systems running IIS Version 5 Web servers. Companies that used IIS Version 5 and failed to apply a recent security software patch, MS04-011, were vulnerable to compromise.

The June attacks also used two vulnerabilities in Windows and the Internet Explorer Web browser to silently run the malicious code distributed from the IIS servers on machines that visited the compromised sites, redirecting the customers to Web sites controlled by the hackers and downloading a Trojan horse program that captures keystrokes and personal data.

The IDG News Service is a Network World affiliate.