One of the more important aspects of business systems security is simply being diligent about applying software updates. Global hackers spend full time at jobs trying to find vulnerabilities in software. As soon as a weakness is found, it is usually just a few hours before that weakness has made it around the world by newsgroup postings and email alerts. This patching has become so common that the second Tuesday of each month is known as patch Tuesday and is the day that Microsoft releases it's monthly software patches.

It is a good idea to also keep updated to known software vulnerabilities as published in reputable sources such as the Internet Storm Center. These sites aggregate vulnerability data together in one list. Besides operating systems, it is also a good idea to make sure that antivirus and anti-spyware programs are updating themselves.  If they aren't, it is usually a sign that there is a deeper problem.