Last month, the EFF faced down a lawsuit claiming that one of its "Stupid Patent of the Month" blog posts illegally defamed the inventor, a patent lawyer named Scott Horstemeyer. Days after the lawsuit became public, it was dropped.

The series hasn't skipped a beat, though, and the newest edition highlights another serial litigator with a ridiculous patent. Wetro Lan LLC believes that its US Patent No. 6,795,918 covers Internet firewalls, or as it says, a system of "filtering data packets" by "extracting the source, destination, and protocol information" and "dropping the received data packet if the extracted information indicates a request for access to an unauthorized service."

"This month’s winner is a terrible patent," writes EFF patent lawyer Daniel Nazer. "But it earns a special place in the Pantheon of stupid patents because it is being wielded in one of most outrageous trolling campaigns we have ever seen."

Nazer points out that the patent was filed in 2000, well after the invention of network firewalls, which date to the 1980s. (And of course, the basic concept of a firewall predates computer technology altogether.) He continues:

Here’s how you get a patent on a firewall more than a decade after firewalls were invented. Step 1: File a description of your so-called invention that is nothing more than mundane details about how firewalls work. Step 2: Add some language saying this is totally not just a firewall. Step 3: Claim a firewall. With any luck, the Patent Office will just wave you through.

"The likely point of this litigation is to extract a nuisance settlement," he concludes. "We have significant doubts that Wetro Lan would ever litigate one of its cases on the merits, and win."

The patent's inventor is Steven Trolan, who didn't respond to a phone message from Ars Technica. Wetro Lan lawyer Austin Hansley—the same attorney who recently dropped his patent lawsuit over photo contests after a challenge from the EFF—also didn't respond to an interview request.

One amazing fact about the Wetro Lan lawsuits is that Trolan actually allowed the patent to expire in 2012. He didn't value it enough to pay maintenance fees on it. But it's still usable in lawsuits because patent damages go back six years. So Wetro Lan can sue in 2015 and still seek to collect damages for the 2009-2012 period before the patent expired.

Wetro Lan has filed dozens of lawsuits, all based in East Texas. It maintains its "headquarters," a small Plano, Texas office suite it shares with several other patent-trolling companies. It has sued big companies like Vizio (PDF) and TRENDnet (PDF), as well as small ones like Hacom, LLC, based in Santa Ana, California. The complaints say that a huge variety of routers and firewall equipment infringe their firewall patent.

It's an outrageous patent campaign, and in the EFF's view is a prime example of why legislative reform in Congress is needed. Even improving case law, like last year's Alice Corp. Supreme Court decision, hasn't stopped the Wetro Lan business model. Without it, "trolls will keep shaking down small companies like Hacom," Nazer states.