The word "spoof" means to hoax, trick, or deceive. Therefore, in the IT world, spoofing refers tricking or deceiving computer systems or other computer users. This is typically done by hiding one's identity or faking the identity of another user on the Internet.
Spoofing can take place on the Internet in several different ways. One common method is through e-mail. E-mail spoofing involves sending messages from a bogus e-mail address or faking the e-mail address of another user. Fortunately, most e-mail servers have security features that prevent unauthorized users from sending messages. However, spammers often send spam messages from their own SMTP, which allows them to use fake e-mail addresses. Therefore, it is possible to receive e-mail from an address that is not the actual address of the person sending the message.
Another way spoofing takes place on the Internet is via IP spoofing. This involves masking the IP address of a certain computer system. By hiding or faking a computer's IP address, it is difficult for other systems to determine where the computer is transmitting data from. Because IP spoofing makes it difficult to track the source of a transmission, it is often used in denial-of-service attacks that overload a server. This may cause the server to either crash or become unresponsive to legitimate requests. Fortunately, software security systems have been developed that can identify denial-of-service attacks and block their transmissions.
Finally, spoofing can be done by simply faking an identity, such as an online username. For example, when posting on an Web discussion board, a user may pretend he is the representative for a certain company, when he actually has no association with the organization. In online chat rooms, users may fake their age, gender, and location.
While the Internet is a great place to communicate with others, it can also be an easy place to fake an identity. Therefore, always make sure you know who you are communicating with before giving out private information.