[narag]

Hiding the source language makes identifying the origin of the malware difficult.

How so? Knowing that it was written using VC would hardly help identifying the origin.

That's not to say that you're wrong about the tool used, but I don't believe the goal was to cover their tracks, but some kind of optimization. Viruses often face space constraints.

[DEinspanjer]

I am not knowledgeable enough to say much on this topic, but I was wondering if maybe such rewriting would also serve to make it easy to mutate code to change its signature?

[lukeschlather]

That was sort of what I was getting at. The obfuscation of the source language may be correlated, but it's not the goal.