Security vendor Barracuda Networks has vowed to defend itself against a patent infringement accusation by Trend Micro.

Barracuda claims to have received repeated requests from Trend Micro to remove ClamAV from its products or pay a licence fee.

ClamAV is a free and open source security application originally developed by Tomasz Kojm in 2001. More than a million unique IP addresses download updates daily.

The software was acquired by Sourcefire, the company that created Snort, in August 2007.

However, Barracuda claims that Trend Micro is seeking to enforce a patent that gives it control of antivirus scanning at the gateway, thereby dragging ClamAV, as a gateway scanning tool, into the row.

"Trend Micro's actions illustrate that ClamAV and other open source projects remain vulnerable to commercial patent holders attempting to hinder the free and open source community," said Dean Drako, president and chief executive at Barracuda.

"Trend Micro appears to be seeking an interpretation of its '600 patent such that it would have exclusive control of gateway antivirus scanning.

"Scanning for viruses at the gateway is an obvious and common technique that is used by most businesses worldwide.

"So this interpretation would mean that anyone, including the owners of the more than one million active ClamAV installations, could potentially be sued by Trend Micro."

Barracuda claims that Trend Micro's subsequent ITC claim alleges that Barracuda infringes on Trend's '600 patent, but effectively implies that any anyone using ClamAV at the gateway infringes on the patent.

Barracuda believes that the patent is invalid due to prior art, and that neither its products nor ClamAV infringe the patent.

"Trend Micro's claim with the ITC is unfounded since the ITC generally oversees import issues," said Drako.

"Barracuda designs and manufactures all of the products in question in the US. We believe that Trend Micro's actions are a blatant abuse of the US legal system.

"Since Trend Micro is a consumer of free and open source software we call on Trend Micro to drop these attacks."