So-called personal firewalls such as ZoneAlarm (http://www.zonelabs.com) and BlackICE Defender (http://www.iss.net/download) offer added protection for individual machines. These are software applications that lock down vulnerabilities on an individual computer, hiding all ports and allowing only user-approved traffic in and out. They are an excellent resource for securing a personal computer and can often be found and used non-commercially free of charge.