Friday, September 30, 2011

The Virus War

In ESIEA, I am doing research on metamorphic viruses.  It is a new area for me, so I have been reading up on lots of new material.  I am fascinated at some of the gambits and defenses that are happening in the war between virus writers and antivirus researchers.

In the past week, I have been experimenting with virus construction kits, octave (free version of matlab), and reading reams of papers on computer viruses, hidden Markov models, etc.  I feel like I am going in about 12 directions at once.  But as my master's thesis adviser once told me, "that's research".

A quick history of viruses...

The classic viruses were fairly easy to detect through a method known as "signature detection".  Essentially, virus scanners look for a bit pattern associated with a virus to identify a corrupted file.  This method is still the predominant one, but newer viruses are being designed to evade this method.

"Encrypted viruses" attempt to evade scanners by encrypting the body of the virus.  Typically, this would be done with a XOR operation, so that the same procedure can be used to both encrypt and decrypt the body of the virus.  By itself, this approach is not especially useful -- the virus scanner can still identify the signature of the encryption/decryption code.

"Polymorphic viruses" improve on encrypted viruses by mutating the decrypter function.  A simple version of the signature detection approach will then fail totally.  Except...  Modern scanners will decrypt the virus body, and then scan the virus.  (I am still a little fuzzy on how they know when to decrypt the virus body.)

But polymorphic viruses point the way to a far more interesting approach.  Rather than relying on encryption, "metamorphic viruses" mutate the body of the virus.  This strategy can evade signature detection approaches without relying on encryption.  (Interestingly, DRM systems are apparently exploring this technique to defy reverse engineering efforts).

Detecting metamorphic viruses is fairly challenging.  Fortunately, most of the metamorphic viruses today have not been particularly good.  But some are.  NGVCK (Next Generation Virus Construction Kit) was designed (apparently) as a proof of concept.  It produces harmless, but hard to detect viruses.  (Its last release was in 2002 -- virus scanners might have caught up to it these days).

Current research has been exploring statistical models, especially hidden Markov Models (HMM).  The results seem promising, but the battle is not over.  Some research suggests that attackers could tune the mutations to emulate benign files.  Virus scanners are then left with the unpleasant choice of rejecting benign files or accepting some malicious files (and probably some of both).

Anyway, it is an exciting new realm for me!

Sunday, September 25, 2011

An American in Laval

After finishing up a fantastic summer at Mozilla, I hopped on board a plane to France to begin my 3 month odyssey abroad.  I was still exhausted from the all hands meeting at Mozilla.  I woke up at 4am to catch the shuttle to the airport, with a layover in Philly, followed by an hour shuttle from Charles de Gaulle to the train station at Montparnasse, followed by a 2 hour train ride to Laval, finally to arrive at my destination at about noon the following day.  I think I am just finally catching up on sleep now.

I have been in France for almost a week, and I've been overwhelmed by my reception.  The people here have been uniformly friendly, and have gone out of their way to make me feel welcome.  The town of Laval is lovely, and the food has been delicious.

The Saturday market in Laval was overwhelming.  In California, we have farmer's markets, but these are pitifully small compared to Laval.  There was fresh-baked bread, giant tubs of paella, seafood so fresh that it was literally trying to escape, and produce that has to be seen to be believed.  I think the produce section alone would be equivalent to 3 or 4 farmer's markets back home.  I think I will enjoy my time here.

So far, the biggest difference that I have noticed is that there is a sharp divide between work and play.  In the states, we buy huge cups of coffee and take them to go so that we can go back to work.  Half the time, 'work' might consist of Facebook and Farmville, but the pressure to be at our desks is very strong.

In France, cups of coffee are small, and no one gets them to go.  You sit and chat with friends, and when you are finished, you go back to work.  And then you work.  I'm not sure who comes out ahead in terms of production, but I am gaining an appreciation for the French approach.