A Personal Firewall is a security technology that protects your personal information from intruders, by keeping unauthorized data from entering or exiting your system, via the Internet or another network. Personal firewall software such as Symantec’s Norton Internet Security, Network Ice’s BlackIce Defender, McAfee’s Personal Firewall and Zone Lab’s free ZoneAlarm can help you monitor intrusion attempts and protect you from most Trojan horse or spy-ware programs that let a hacker control your computer over the Internet. They are available either as part of an integrated security suite or as stand-alone software.