A spam filter is a piece of software that is installed on an email server and keeps track of all inbound emails in order to hinder any unwanted ones from reaching a given mailbox. A few instances of such emails would be: offers for pills or money, fraudulent bank statements or attachments that contain malicious code sent with the intention to infect your computer. Email filters typically examine the content of an email and when they come across particular keywords or other suspicious content, they either delete the message or re-send it to the Spam/Junk folder instead of the Inbox folder. Some web hosts mix their own spam filters with up-to-date databases from spam-detecting organizations, so as to ensure higher levels of protection for their customers. Such databases contain patterns, mail server IPs and other information about spam messages recently uncovered by these organizations.