"What do we do about malware? The long term solution, at least for managed networks like enterprises, may be whitelisting. But in the meantime we’re still drowning in new variants every day. In the 2009 generation of their products Symantec is trying a new approach: file reputation.
It’s a little early to tell if it works well enough but it seems to me to have potential. The classic methods of malware scanning are generally agreed to be unsustainable. It’s not feasible for malware companies to have a signature for every new variant, and yet we should expect the products to work even the first time a file appears on a customer’s system. For this reason heuristics are employed, but they have limits. " – Content courtesy of Malware Detection Goes Hybrid