A spam filter is a piece of software that runs on a POP3/IMAP mail server and monitors all inbound email messages to prevent any unwanted ones from entering a particular mailbox. A few instances of such emails would be: offers for pills or cash, fraudulent banking notices or attachments that contain malicious software sent with the idea of infecting your personal computer. Spam filters usually examine the content of an email and in case they detect some keywords or other suspicious content, they either delete the email message or re-send it to the Spam/Junk folder instead of the Inbox folder. Certain hosting providers mix their own spam filters with up-to-the-minute databases from spam-tracing organizations, so as to guarantee higher levels of safety for their clients. Such databases include patterns, email server IP addresses and other info about spam email messages recently reported by these organizations.