The Applescript.THT Trojan Horse is a piece of malware that is currently being distributed through iChat and Limewire. (Mac OS X 10.4 & Mac OS X 10.5) It is currently being distributed as a compiled Applescript ASthtv05 (60kb size) and a app called AStht_v06 (3.1mb). You must download one of these to become infected. Once running the Trojan can be found in the Library/Caches folder and add itself to the System Login Items and will turn on File Sharing, Web Sharing and Remote access. What does this mean to you ? Essentially someone can turn on your iSight camera and take pictures, log keystrokes, send and receive files, take screen shots….you get the point !?! Hackers are taking advantage of Apple Remote Desktop Agent security hole. The ARDAgent accepts commands from Applescript the (scripting language in OS X) The script will allow any user to install programs on the root level of the operating system regardless of their access privileges.
I think the moral of the story is we as MAC users need to start being aware that viruses do exist and as the popularity grows so will the threat.