A spam filter is a piece of software that runs on a POP3/IMAP email server and keeps track of all inbound emails to hinder any undesirable ones from reaching a certain mailbox. A few examples of such email messages would be: offers for pills or cash, fraudulent bank statements or attachments that contain malware sent with the idea to damage your personal computer. Email filters typically ‘scan’ the content of an email message and when they detect some keywords or other suspicious content, they either erase the email message or re-send it to the Junk/Spam folder instead of the Inbox folder. Some hosting companies mix their own email filters with up-to-the-minute databases from spam-detecting organizations, so as to ensure higher levels of security for their customers. Such databases include patterns, email server IP addresses and other info about spam emails recently uncovered by these organizations.