A spam filter is a software app that is installed on a POP3/IMAP mail server and ‘scans’ all incoming email messages so as to hinder any unwanted ones from entering a certain mailbox. Several examples of such email messages would be: offers for pills or cash, fake bank notifications or attachments that contain malware sent with the intention to damage your personal computer. Spam filters normally check the content of an email message and when they spot specific keywords or other dubious content, they either delete the message or re-send it to the Spam/Junk folder instead of the Inbox folder. Some web hosting providers mix their own email filters with up-to-the-minute databases from spam-tracking organizations, so as to ensure better security for their clients. Such databases include patterns, mail server IPs and other information about spam email messages recently uncovered by these organizations.