Spam is unsolicited e-mail on the Internet. Spam messages are sent out in many forms usually to solicit fake applications in an effort to gain money from computer users who fall for the spam tricks. Spam may be classified as other types of messages sent with malicious intent or with the purpose of fraudulent monetary gain. Spam messages may spread dangerous programs or files to computer users through attachments or malicious links. Spam messages may be sent out in various forms such as Internet forum spam, junk fax transmissions, instant messaging spam, Web search engine spam, spam in blogs, Usenet newsgroup spam, wiki spam, and mobile phone messaging spam.