This isn't just any hacker crew; its targeting of defense subcontractors means it could easily undermine the integrity of the world's weapons.

This new crew, dubbed Icefog by Kaspersky Lab, is small and nimble, and it appears to know exactly what it wants to steal from its victims. Unlike some other advanced hacker outfits that linger on victims' networks for months or years after gaining access, the Icefog crew doesn't stick around waiting to get caught.

"They will infiltrate an organization. They know exactly what they are looking for, pull it out, and as soon as they complete their assignment they move on -- they actually clean things up and move on," said Kurt Baumgartner, a security researcher with Kaspersky, during a speech in Washington today.