- In 1995, Trend Micro filed for a patent "for detecting and selectively removing/viruses in data transfers". Basically, any method that can detect when a file might be infected by a virus, when you are sending that file from one computer system to another.
- Trend Micro is awarded patent #5,623,600 in April 1997.
- In May 1997, Trend Micro sues McAfee Associates (another anti-virus maker) for patent infringement.
- Settled in 2000.
- In May 2004, Trend Micro sues Fortinet over same patent.
- Settled in 2006.
- In 2006, Trend Micro claims open-source anti-virus product ClamAV infringes on this patent.
- Barracuda Networks (which creates enterprise anti-virus solutions, using ClamAV in some of its products) brings action against Trend Micro.
- In 2008, Fortinet also brings action against Trend Micro.
On May 19 of this year the examiner issued a Final Rejection [PDF], denying all of the claims in the '600 patent, except claims 10 and 13, including those claims that Trend Micro proposed to add through amendment. So out of 22 original claims and 15 added claims, Trend Micro now is left with just two claims. Of course, this is still not the end. Trend Micro has two months in which to respond to this Final Rejection, and even after that point it will have further avenues of appeal. However, the evidence mounted against the '600 patent is substantial and will not be easily overcome.