3.Antivirus Problems. About 1.2 percent of the computers in the Promisec survey had problems with their antivirus software, usually in the form of out-of-date signature files.

With the major antivirus vendors releasing between 1200 and 2400 updates per week (a more accurate figure than the number of new viruses, even though the numbers of viruses and updates don't match), it's important to keep protection current. This is particularly true because one infection strategy used by malware authors is to infect as many computers as possible in the shortest possible time before the protectors can respond. For example, on July 19, 2001, the Code Red worm infected 359,000 computers in 14 hours.

Ironically, Code Red attacked a vulnerability in Windows that had been patched more than two years earlier.

4.Outdated Microsoft Service Packs. Running Windows without the latest updates is another major problem. About 1.5 percent of the surveyed computers had failed to update the operating system to the most current service pack.

Keeping your software current is Basic Security 101 and every company tries to do it, most commonly by doing automatic updates.

However, it's a big job to cover every desktop in the company, not to mention the laptops, PDAs and mobile phones that connect to the network. Stuff slips through the cracks, and again, it takes only one endpoint with a known security flaw to compromise the entire network.

Windows service packs are a special problem, because some software inevitably has problems with them. In the case of Service Pack 2, Microsoft acknowledged that 50 major applications initially wouldn't run with it, primarily because SP2 turned on the firewall by default. It usually takes weeks or months after Microsoft releases a service pack before all the vendors are singing off the same page.

If your users need software that stops working when a new service pack comes out, a common solution is to "temporarily" forgo installing the service pack until the software company catches up. That means going back through later and checking that those systems are updated when it becomes possible - if you remember.