Is Antivirus Dead?

By Bruce Schneier
Information Security
November 2009

This essay appeared as the second half of a point/counterpoint with Marcus Ranum. Marcus's half is here.

Security is never black and white. If someone asks, "for best security, should I do A or B?" the answer almost invariably is both. But security is always a trade-off. Often it's impossible to do both A and B--there's no time to do both, it's too expensive to do both, or whatever -- and you have to choose. In that case, you look at A and B and you make you best choice. But it's almost always more secure to do both.

Yes, antivirus programs have been getting less effective as new viruses are more frequent and existing viruses mutate faster. Yes, antivirus companies are forever playing catch-up, trying to create signatures for new viruses. Yes, signature-based antivirus software won't protect you when a virus is new, before the signature is added to the detection program. Antivirus is by no means a panacea.

On the other hand, an antivirus program with up-to-date signatures will protect you from a lot of threats. It'll protect you against viruses, against spyware, against Trojans--against all sorts of malware. It'll run in the background, automatically, and you won't notice any performance degradation at all. And -- here's the best part -- it can be free. AVG won't cost you a penny. To me, this is an easy trade-off, certainly for the average computer user who clicks on attachments he probably shouldn't click on, downloads things he probably shouldn't download, and doesn't understand the finer workings of Windows Personal Firewall.

Certainly security would be improved if people used whitelisting programs such as Bit9 Parity and Savant Protection--and I personally recommend Malwarebytes' Anti-Malware--but a lot of users are going to have trouble with this. The average user will probably just swat away the "you're trying to run a program not on your whitelist" warning message or--even worse--wonder why his computer is broken when he tries to run a new piece of software. The average corporate IT department doesn't have a good idea of what software is running on all the computers within the corporation, and doesn't want the administrative overhead of managing all the change requests. And whitelists aren't a panacea, either: they don't defend against malware that attaches itself to data files (think Word macro viruses), for example.

One of the newest trends in IT is consumerization, and if you don't already know about it, you soon will. It's the idea that new technologies, the cool stuff people want, will become available for the consumer market before they become available for the business market. What it means to business is that people -- employees, customers, partners -- will access business networks from wherever they happen to be, with whatever hardware and software they have. Maybe it'll be the computer you gave them when you hired them. Maybe it'll be their home computer, the one their kids use. Maybe it'll be their cell phone or PDA, or a computer in a hotel's business center. Your business will have no way to know what they're using, and -- more importantly -- you'll have no control.

In this kind of environment, computers are going to connect to each other without a whole lot of trust between them. Untrusted computers are going to connect to untrusted networks. Trusted computers are going to connect to untrusted networks. The whole idea of "safe computing" is going to take on a whole new meaning--every man for himself. A corporate network is going to need a simple, dumb, signature-based antivirus product at the gateway of its network. And a user is going to need a similar program to protect his computer.

Bottom line: antivirus software is neither necessary nor sufficient for security, but it's still a good idea. It's not a panacea that magically makes you safe, nor is it is obsolete in the face of current threats. As countermeasures go, it's cheap, it's easy, and it's effective. I haven't dumped my antivirus program, and I have no intention of doing so anytime soon.

I don't even want an Xbox.

earlier essay: Beyond Security Theater
later essay: Reputation is Everything in IT Security
categories: Computer and Information Security
back to Essays and Op Eds

Photo of Bruce Schneier by Per Ervland.

Schneier on Security is a personal website. Opinions expressed are not necessarily those of Co3 Systems, Inc..