Even with patches, anti-virus software, firewalls and intrusion-detection systems, our Windows systems are getting infected by new viruses and worms. What other defense can we use?To combat the recent Sasser worm, visit Microsoft's\u00a0Sasser scanning Web page.The tool will identify whether a PC is infected and remove the worm if it is found. You have to install the\u00a0MS04-011 patch\u00a0before the tool will work.To provide additional protection, the free Qwik-Fix tool from www.pivx.com is helpful. Qwik-Fix adjusts Windows security settings to block a number of holes in Windows features that most users do not use. Vulnerabilities addressed by Qwik-Fix include IE Zone crossing exploits, RPC\/DCOM problems, HTA mime-type abuse, Windows Messenger desktop spam, Stream File writing and Trojan services, and protocol handler problems. The program supports systems running Windows 95 through 2003 Server and provides for automatic updates.Other tools can be found at www.grc.com. The site's online port-scanning services can provide information for further tightening your network controls. Consider configuring your Windows systems to automatically perform Windows Updates installation as well.