Learning About Local Scanning Utilities
In addition to Nessus, the Open Source product mentioned earlier in this article, there are numerous vendors who offer outstanding security scanning software. For organizations large enough to support network management teams and software, security scans are often integrated into those environments. You may want to talk to your network management vendor about products or tie-ins that your existing environment can support. Otherwise, you'll find plenty of products to like. In my own experience, I've had the best luck with the following products:
Internet Security Systems (ISS) makes a whole family of security scanning products targeted at specific types of servers, systems, and networks. Especially noteworthy are Online Scanner, RealSecure, and other SAFEsuite components.
Network Security Systems LANPatrol provides you with a scanning tool you can use to perform both internal and external network security audits. Like ISS products, LANPatrol does a good job of checking networks for potential vulnerabilities.
PGP Security (a division of Network Associates) CyberCop Scanner and related products combine a powerful security scanner with state-of-the-art intrusion detection systems.
Pedestal Software's Security Expressions product is the best way we know of to analyze existing platforms for security problems, but also to check to be sure that a formal security policy has been properly implemented on machines as they're scanned.
NetIQ's Security Analyzer scans Windows, Sun Solaris, and Red Hat Linux operating systems, and does a good job with all of them. It's also one of the lowest cost options presented here.
If you purchase a local scanning utility, you'll still need to upgrade its attack library regularly (just as you should any kind of security tool), but scanning will be under your control and at your discretion. One final tip: check out Talisker's Network Security Tools, it has the most comprehensive listing of available scanners I've ever seen.