Most IP addresses are listed as a result of directly sending spam or viruses to the Barracuda Reputation System's detectors. The Barracuda Reputation System detects spam by using honeypots, special addresses created to receive only spam and do not belong to any real user and through analysis of captive spyware protocol activity. In addition, the BRBL leverages some data derived from the Barracuda Blocklist (BBL) that is delivered to Barracuda Spam & Virus Firewalls as part of Barracuda Networks' product offerings.