While the company's system administrators spend much time thinking about the corporate firewall systems for employee-house, the vulnerability that is often overlooked is the remote computer system protected employees, who are not protected computer mobile laptop users (employees on the street) and all but the network unprotected handheld device. Yeo then describe the methods used by the firewall protection in general - a proxy server firewall, packet filtering, signature-based firewalls and stateful inspection based firewalls while examining the strengths and weaknesses of each type. He then explains how each type of protection method implemented in the firewall "private", a variety of products including Black Ice Defender, Zone Alarm, which uses the Linux iptables firewall method is given, and pros and cons of these methods rely on the personal firewall.