New Russian Malware HAMMERTOSS

FireEye has a detailed report of a sophisticated piece of Russian malware: HAMMERTOSS. It uses some clever techniques to hide:

The Hammertoss backdoor malware looks for a different Twitter handle each day -- automatically prompted by a list generated by the tool -- to get its instructions. If the handle it's looking for is not registered that day, it merely returns the next day and checks for the Twitter handle designated for that day. If the account is active, Hammertoss searches for a tweet with a URL and hashtag, and then visits the URL.
That's where a legit-looking image is grabbed and then opened by Hammertoss: the image contains encrypted instructions, which Hammertoss decrypts. The commands, which include instructions for obtaining files from the victim's network, typically then lead the malware to send that stolen information to a cloud-based storage service.