MiniDuke delivers a secret software program, via an infected PDF file that monitors PCs it gets into, that passes back keyboard activity and files to servers in Panama and Turkey. MiniDuke is unique in terms of the attention paid to keeping its presence secret from network security systems. MiniDuke stays dormant until it senses it is not being monitored, then seeks out a specific Twitter feed that the hacker uses to communicate with infected machines.
MiniDuke carried out its attack using an official looking email, with a PDF file attached, sent to specific individuals. It is an email the recipients were not expecting. This is known in the trade as "spear fishing" (or "spear phishing"), which is a Cyber War technique that sends official looking email to specific individuals with an attachment which, if opened, secretly installs a program that sends data from the email recipient's PC to the spear fisher's computer. In the last few years an increasing number of military, corporate, and government personnel have received these official-looking emails with a PDF document attached and asking for prompt attention.
MiniDuke is one of the most sophisticated spear phishing attacks seen so far. It shares some characteristic of professional American–Israeli efforts like Duqu but also incorporates some new ideas (heavy use of Twitter, a very gradual infection process, and lots of scouting). It’s unclear where it came from, or at least no one has released any information on that yet. This may mean that the author has been identified and the police are closing in. Or probably not, as MiniDuke appears to be the result of a major effort.