IP Address

An Internet Protocol address (or IP address) is the specific network address of a computer consisting of four numbers separated by periods (e.g., 192.168.0.1). If you know the name (hostname) of the system you can find the IP number using a nslookup utility or site such as http://www.webreference.com/cgi-bin/nslookup.cgi

For e-mail messages, it is important to look at the full headers of the message to find the IP number(s) of the system(s) that sent the message, since hostnames used in e-mail are often forged.