The net community has cut off the infection mechanism of a trojan, called Xombe, which poses as a Windows XP security update.
Xombe, the latest in a string of backdoor programs designed to compromise Windows PCs, is capable of stealing passwords or turning compromised machines into components of an attack network under the control of unknown crackers.
The Xombe trojan downloader was sent as an email to a large of people (probably using spamming software) last Friday. Like the Swen worm, infectious emails contaminated by Xombe pose as a Windows security update. The ploy aims to fool the unwary into running malicious code (contained in an infectious attachment).
In the case of Xombe, the infectious payload is designed to download another Trojan from the net and to load this malware onto a victim's computer.
The site housing this trojan (gamemaniacs.org) was disabled on Saturday, according to Finnish AV firm F-Secure. Even so, infected machines still need hosing down. Also, users should still be wary of suspicious- looking emails in their in-boxes.
Infectious emails appear to come from email@example.com, containing the subject line: "Windows XP Service Pack 1 (Express) - Critical Update".
The trojan has three components: a first-stage downloader that comes in infectious email (winxp_sp1.exe); the main component of the trojan - a general-purpose downloader application controlled via a Web page (msvchost.exe) and a HTTP client - designed to conduct DDoS attacks (http_f.dll).
AV firms disagree about the severity of the risk posed by Xombe, depending on how many reports from their clients each has received about the latest Windows nasty.
To defend against Xombe, users should update their AV signature definition files to recognise the virus and to resist the temptation to open suspicious looking emails. ®