A worm which spread from infected Microsoft Internet Information Services (IIS) web servers in June is using instant messages (IMs) and infected websites in Russia, Uruguay and the US to spread itself.
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Researchers at PivX Solutions have intercepted new malicious code that closely resembles widespread attacks in June attributed to a malicious computer code named "Scob" or "Download.ject".
The latest attacks use mass-distributed instant messages to lure internet users to websites that distribute malicious code similar to Download.ject, said Thor Larholm, senior security researcher at PivX.
First detected on 24 June, the Scob attacks were 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 websites controlled by the hackers and downloading a Trojan horse program that captures keystrokes and personal data.
The attacks begin with instant messages sent to customers using America Online's AOL Instant Messenger (AIM) or ICQ instant message program. The messages invite recipients to click on a link to a web page, with pitches such as "Check out my new home page!" The messages could be sent from strangers or from regular IM correspondents, or "buddies", Larholm said.
Once victims click on the link, they are taken to one of a handful of attack web pages hosted on servers in Uruguay, Russia and the US, from which a Trojan horse program is downloaded.
In addition to opening a "back door" on the victim's computer through which more malicious programs can be downloaded, the new attacks change the victim's web browser home page or Outlook e-mail search page to websites featuring adult content, Larholm said.
PivX is still analysing the attacks to see if malicious code is placed on victims' machines, but many of the files used by the new worm and the way in which the attacks are being carried out point to the same group that launched the Scob attacks in June, Larholm said.
"The code is different enough to be something of its own, but unique enough to be related," he said. "And as with the Scob attacks, this is all about money - in this case, driving ad revenue for specific people."
The attack websites take advantage of vulnerabilities in Explorer and Outlook that Microsoft has patched, but that allow the attackers to place and run malicious code on unpatched systems. Two patches from 2003, MS03-025 and MS03-040 address the flaws used by the new worm, Larholm said.
Anti-virus companies were informed of the new malicious code but did not have virus signatures issued.
Paul Roberts writes for IDG News Service