If your servers’ services are exposed in one way or another to the Internet, having a reputable IT security firm run a scan on them might be a good idea.
Qualys, a company specializing in vulnerability management, just launched a free service allowing you to scan any box that has a public IP address for the 20 most dangerous vulnerabilities affecting networks worldwide. If any of the vulnerabilities are discovered within your systems, the scanning engine will provide you with a detailed report describing what must be done to rectify the situation.
My servers were spotless, but I’ve used Qualys services in the past, and I know that when they say they can do something, they do it well.
The only problem I’ve experienced with them is with their marketing people. They’re a bit too persistent for my taste. So if they call you and want to sell you something, be nice with them and tell them you’re not interested right away, else they’ll drag on the conversation on and on and on…