The root of the legal dispute is a patent by Trend Micro covering an anti-virus solution in combination with a firewall or gateway. The opponent in the legal dispute is the security vendor Barracuda, which uses the free ClamAV anti-virus software in its own products.

The disputed Trend Micro patent #5.623.600 from 1995 describes the technology in a very generic way stating that the 600 patent searches the network gateway for viruses and other undesirable software. At the same time, because viruses can be embedded in content (such as email attachments and other web content), the 600 patent searches the content.

Software patents of this kind, which are often referred to as trivial due to their generic wording, are contentious in Europe, but a generally accepted business basis in the USA. Barracuda Networks is looking to contest the patent and regards the current case as a precedent in which it calls on the Open Source community to give support.

Under US legislation a patent can be declared invalid if the contester is able to prove that the technology it describes was known as prior art to the patent being assigned. This is why Barracuda Networks is looking for comprehensive evidence of this prior to September 26 1995, the date on which Trend Micro applied for its patent. The prior art in this case mainly comprises an antivirus scanner in combination with a firewall or a gateway. This could be software code, but also advertising material, other publications, or references to websites. Barracuda Networks has set up a separate website which describes both the legal dispute and the material sought for.
Barracuda Networks submitted an action for declaratory judgment in the spring of 2007 with the aim of having the patent ruled invalid. In response, Trend Micro submitted a counter claim. November 20, Trend Micro contacted the US International Trade Commission (ITC) and submitted a claim agains Barracuda and a second company, Panda Software International, with the aim of securing license payments or forcing the two companies to discontinue use of ClamAV. Trend Micro describes the object of the claim as follows: "ClamAV software is written, at least in part, by ClamAV developer team members located in Europe and Australia". Trend Micro thus concludes that the contentious software is imported by Barracuda, and the ITC can only rule on questions concerning imported goods. In a recent press release, Barracuda's CEO, Dean Drako responded saying: "Barracuda Networks designs and manufactures all of the products in question in the United States." The ITC would thus be the wrong address for the complaint, and Barracuda could again focus on its original objective of attempting to invalidate the software patent.