Barracuda Networks is to open its spam blocking list for companies to use free of charge.

The Barracuda Reputation Block List (BRBL) is a dynamically updated list of known spam servers that can be used to block spam at the gateway.

This means that companies do not have to run all incoming email though antivirus scanners and other filtering technologies, according to the firm.

"Most IP addresses are listed as a result of directly sending spam or viruses to the Barracuda Reputation System detectors," said the company in a statement.

"The system detects spam by using 'honey-pots', special addresses created to receive only spam and which 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 Block List that is delivered to Barracuda spam firewalls as part of Barracuda's product offerings."

The BRBL is now available for free download and includes a tool to report other spam servers.

This is not the first time that Barracuda has given away security software. The company is currently being sued by Trend Micro for giving away its Clam antivirus engine without paying a licence fee for a patent which Barracuda is challenging.