A spam filter is a software program that is designed to identify and block unwanted emails, commonly known as spam. The primary function of a spam filter is to distinguish between wanted email messages (ham) and unsolicited bulk email messages (spam). It does this by using various techniques such as analyzing the content of an email message, checking its sender's reputation or IP address, and looking for patterns associated with known spammers. Once a message has been identified as potential spam, it is either sent to a separate folder designated for spam emails or blocked entirely from reaching the recipient’s inbox. Spam filters are commonly used by email service providers to protect their users from unwanted messages and reduce the amount of junk mail that ends up in people's inboxes.