Spoofing is a technique of fooling a computer network into believing something is happening which isn't. Email spoofing is one popular form of spoofing where a hacker can send email to people from a false email address. One hacker trick it to send emails pretending to a network adminitors asking for people's passwords as the computer network is experiencing errors and has deleted the password file. Spoofing usually involves making packets / messages seem to be sent from authorized IP addresses.