Following months of legal communications with Barracuda Networks, Trend Micro is suing its rival over its use of ClamAV — a product maintained by US open-source company Sourcefire — on the grounds that Barracuda Network's use of the software in some of its products infringes a patent held by Trend Micro on applying antivirus software via gateway proxy servers.
Trend Micro alleges that ClamAV has allowed Barracuda's products to operate in a way that infringes a patent granted to the company in 1997.
"Trend Micro was the first company to extend antivirus protection from the desktop to gateways and servers, and the patent — co-authored by the company's chief executive Eva Chen in 1997 — reflects and protects these vital technical advances," the company said in a statement in 2005 after the US International Trade Commission ruled against another security company, Fortinet, for infringing on the same patent.
The patent stakes a claim to antivirus software capturing viruses at the gateway through the use of file transfer protocol (FTP) and simple mail transfer protocol (SMTP) proxy servers for web and email virus filtering respectively.
Since 2006, Barracuda Networks has been receiving communications from Trend Micro's legal team requesting Barracuda either pay licence fees when using ClamAV, or stop incorporating the software into its products, according to Barracuda's chief executive and president, Dean Drako.
Drako claimed he had tried to contact Trend Micro's legal department but that his attempts had been ignored.
Richard Stallman, founder of the GNU Project and the Free Software Foundation, called Trend Micro a "despicable predator" for its actions.
"This attack is an example of the threat that software patents impose on all software developers: at any moment, you can get sued for using code with the author's permission, or even for the code you wrote," Stallman said in a commentary on Linux.com.
Barracuda also made the claim that open source software is under threat by software-patent holders.
"Trend Micro's actions illustrate that ClamAV and other open-source projects remain vulnerable to commercial patent holders attempting to unjustly hinder the free and open-source community," said Drako in a statement.
However Trend Micro's legal team claim that the case is not against open source but about stopping another company profiting from its intellectual property.
In response to Trend's initial legal salvos, Barracuda filed for a declaratory judgement with the US Federal Court last year, attempting to invalidate Trend Micro's patent.
"Trend Micro appears to be seeking an interpretation of its... 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 utilised 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," said Drako.
ZDNet.co.uk's Tom Espiner contributed to this article.