All computer security defense ultimately comes down to managing risk. Security admins implement various defenses, each of which should have its own cost/benefit analysis. The cost of the defense should not outweigh the estimated damage of the attack or exploit. For example, if buying anti-malware software for a 100 PCs costs $3,900 per year, but cleaning up the damage from a malware attack would cost only $2,000 per year, implementing the anti-malware software wouldn't make sense.

On the other hand, perhaps it would be reasonable to deploy anti-malware only on an external gateway server for the cost of $1,500 per year while being prepared to absorb the potential $250 cost of cleaning up a PC that gets infected by a USB storage stick. Computer security is rarely a binary decision -- it's shades of gray analyzed across the spectrum using risk analysis.

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Lately, while working on several forthcoming product reviews, I've come across some software products that make risk assessment easier to visualize and to present to management. Probably the best example is Bit9's Parity whitelisting application-control program. Parity comes with a service that automatically recognizes 5 billion different files (according to Bit9) based upon their hash signature and other file attributes. Parity can recognize every relatively recent file made by Microsoft, Adobe, and Macromedia, as well as waves of lesser-known programs, including common hacking tools, such as Nmap, Pwdump, Cain & Abel, and so on.

Here's how it work: Parity first compares computers to a baseline "gold standard" image established by the administrator. As users install new software (or malware exploits), Parity is able to calculate a "drift" score for the computer. By accumulating all the drift scores for all the computers on the network, Parity can calculate an aggregate drift score.

Even better, Parity also calculates a file's threat risk. For example, if it were to find a new text editor, it would give the program a low threat rating, because it's unlikely to be involved with an exploit. But if Parity discovers an unauthorized peer-to-peer or popularly exploited program, that program's risk rating would be higher. And if it happens upon a hacking tool -- say pwdump, used to dump Windows password hashes -- that program would have a high risk rating, as would any identified malware program.