"A surprising number of governments are now deploying their own custom malware and the end result could be chaos for the rest of us, F-Secure's malware chief Mikko Hypponen told the TrustyCon ( https://www.trustycon.org/ ) conference in San Francisco on Thursday.
'Governments writing viruses: today we sort of take that for granted but 10 years ago that would have been science fiction,' he told the public conference. 'If someone had come to me ten years ago and told me that by 2014 it will be commonplace for democratic Western governments to write viruses and actively deploy them against other governments, even friendly governments, I would have thought it was a movie plot. But that's exactly where we are today.'
http://www.scmagazine.com/trustycon-malware-expert -mikko-hypponen-kicks-off-conference-on-trust/arti cle/336089/"
there may be lots of different distributions and configurations, but the kernel is a common weak point (single point of failure).
Not only that, but the core userland is pretty much the same stuff across Linux distros, with minimal customization.
It would be an incredibly lucky coincidence if those slight distro-specific tweaks would somehow end up neutralizing the exact piece of malware to reach your machine.