Avast! is offering a free antivirus solution for the Mac. It’s designed to combat the Flashback Trojan, says Jiri Sejtko, director of Avast Virus Lab operations.

The Flashback Trojan linked to the Mac botnet is a derivative of last year’s DevilRobber Mac OS X Trojan. The Avast Virus Lab now has 18 variants of this malware in its antivirus database.

Avast! Free Antivirus for Mac (http://macte.ch/OKxhD) is currently in the late  beta stage. It includes the latest avast! antivirus engine, three shields (Web, File, and Mail) and the WebRep reputation and anti-phishing plugin for Safari browser.