Barracuda Networks plans to focus on finding prior art to defend itself and the open-source ClamAV project against patent claims by rival antivirus vendor Trend Micro, which stressed Tuesday that it owns a tested and valid patent.

Barracuda, facing a Trend Micro complaint before the U.S. International Trade Commission (USITC), will work on showing the agency that other companies used gateway antivirus scanning before Trend Micro received its patent in 1997, Barracuda said Tuesday. Barracuda uses ClamAV code in some of its products.

"In their claim, Trend Micro is seeking an interpretation of its ... patent such that would give it exclusive control of gateway antivirus scanning," said Kylie Heintz, spokeswoman for Barracuda.

"We believe that neither our products, nor the free and open-source ClamAV software, infringe the patent, and further we believe that the patent itself is invalid due to prior art," Heintz said.

The USITC launched a formal investigation of the patent claims in December.

Barracuda's announcement that it intended to find prior art spurred action in the open-source community. Early Tuesday, Groklaw, a blog focused on open-source legal issues, posted an announcement asking for help finding prior art.

But Trend Micro, which filed the USITC complaint in November, has a "known and time-tested patent," said Michael Sweeny, a spokesman for Trend Micro. The company won a similar dispute with rival Fortinet before the USITC in May 2005, Trend Micro noted. Fortinet later settled the patent claims, getting a license from Trend Micro.

In addition, Trend Micro filed a similar complaint against Panda Software International and Panda Distribution, which use a proprietary software package, said Mark Davis, Trend Micro's outside counsel. Trend Micro has not targeted the ClamAV project, he said. "This is purely against commercial competitors," Davis added.

Commercial software vendor Sourcefire purchased the ClamAV project in August. Sourcefire declined to comment on the patent dispute.

Open-source software is not the issue in the USITC complaint, Sweeny added. "We can't see how this would negatively impact open-source development," he said.

Barracuda CEO Dean Drako called scanning for viruses at the gateway "an obvious and common technique" used by most businesses. Almost anyone, including the owners of more than 1 million ClamAV installations, could be sued by Trend Micro if the company's patent claims hold up, he said in a statement.

Barracuda, maker of hardware containing cybersecurity products, has won support in the dispute from the Software Freedom Law Center, a group working to protect open-source software. The law center is grateful to Barracuda for fighting the patent, said Eben Moglen, the center's founding director. "Collective defense from software patents is a shared responsibility for everyone in the free software ecosystem," he said in a statement.

Barracuda has a pending lawsuit seeking to invalidate the patent in the U.S. District Court for the Northern District of California, San Jose division.

Trend Micro is misusing the USITC because it's filing a trade complaint asking the agency to bar importation of a product against a company based in the U.S., Barracuda added. "Barracuda Networks designs and manufactures all of the products in question in the United States," Drako said in his statement. "We believe Trend Micro's actions are a blatant abuse of the U.S. legal system."

But Trend Micro said the USITC is an appropriate venue for the patent complaint. The 2005 Fortinet ruling was also against a company based in the U.S., Davis said. "There appear to be several components that are imported," he said.

Trend Micro's USITC complaint says Barracuda uses code from ClamAV, which is written in part in Europe and Australia. Barracuda also imports hardware components, the complaint says.