Barracuda Central maintains a history of IP addresses for both known spammers as well as senders with good email practices. This information contributes to the Barracuda Reputation System, which gives the Barracuda Spam & Virus Firewall the ability to block or allow a message based on the sender’s IP address. In addition to IP reputation, the Barracuda Central team maintains reputation on URLs, which gives the Barracuda Spam & Virus Firewall the ability to quickly block an email based on a poorly-rated URL contained in the message. By combining both the IP and reputation data, Barracuda Networks can easily determine whether a message is spam or legitimate email. Once identified, Barracuda Central can implement countermeasures to mitigate these threats.