Leap.A is a binary file compiled for Mac OS X. It arrives in an archive file, called ‘latestpics.tgz’. When the executable in the archive is opened the virus activates. First it drops an icon resource and an external hook bundle which is used for spreading through iChat.
Spreading through iChat
Leap.A installs a bundle to ‘~/InputManagers/apphook’ that hooks certain iChat functions. When any of the user’s buddies change their status, the worm initiates a file transfer and sends a copy of ‘ ‘latestpics.tgz’. The file transfer is not visible to the user as the worm hides the transfer status information.
The worm enumerates all applications on the computer that were used during the last month. Leap.A replaces the main executable of those applications with itself and saves the original file to a resource fork with the same filename. When the application is opened the worm activates first, then it runs the original application from the resource fork.
Thanks to F-Secure.