If you get an email from [email protected] with a link to Internet Explorer 7 Release Candidate 1, don't go there: A trojan downloader will get installed and set up a backdoor into your computer.

The spoofed message's link takes you to a site that looks convincingly similar to a Microsoft page, but don't be fooled. The trojan installs via an IE browser vulnerability, according to SurfControl, which is tracking the malicious message and its spread around the Net. The scam is especially timely -- Microsoft today released IE7 for Windows XP. (See Anti-Malware Tools Trip Up IE7 Install.)

Downloaders are among the most prolific types of trojans today and are popular with spammers because they are relatively small pieces of code. Their job is to avoid detection and typically to disable AV and firewalls and then download more malware code. (See Most Popular Trojans.)

— Kelly Jackson Higgins, Senior Editor, Dark Reading