The three biggest patent trolls of this year will all soon face new legal challenges to their most valuable "inventions."

Unified Patents, a company that focuses on invalidating patents through the use of the inter partes review (IPR) process, has filed challenges against patents belonging to the three most litigious "non-practicing entities" of 2016. In late June, the company challenged Uniloc's patent on DRM. Last week, it filed papers against a company called Sportbrain Holdings, which makes wide patent claims over fitness tracking devices. On Monday, Unified challenged Shipping & Transit LLC, formerly known as ArrivalStar, a company that has demanded payments from hundreds of small companies—and even city transit systems—for using GPS vehicle tracking or sending package tracking numbers in e-mail.

The IPR process, created in 2012, has proven effective at knocking out patents that the Patent Office says shouldn't have been issued in the first place. Many private companies have used IPRs, as have third-party organizations like the Electronic Frontier Foundation, which challenged the podcasting patent.

Unified Patents works by selling memberships to companies that are frequently subject to patent claims. It then looks for the most problematic patents in certain industry "zones," like cloud computing, and files IPRs seeking to invalidate those patents.

“Unified’s mission is to disrupt and deter invalid patents used by NPEs from technology sectors we protect," said Unified CEO Kevin Jakel in an e-mail to Ars. "Top filers demonstrate the worst behavior by often going after small companies who do not have the resources to defend themselves. We hope this sends a message that even if they sue small, defenseless companies, patent trolls will no longer be allowed to profit on invalid patents in the tech sector."

The three NPEs targeted by Unified Patents have sued more than 200 companies this year, and their lawsuits account for more than 15 percent of total patent litigation against high-tech companies, according to Unified Patents statistics. Shipping & Transit, aka ArrivalStar, may be one of the most aggressive patent trolls of all time, with its tracking patents being used in more than 450 lawsuits since 2010.

DRM was invented when?

Each of the three patent campaigns is based on its own fanciful history of technology.

The hundreds of demand letters from Shipping & Transit tell the story of inventor Martin Kelly Jones, who conceived his inventions "on a rainy, foggy Atlanta morning" in 1985. The idea was to create a vehicle tracking system combined with automated calling, which would notify parents of school children when a school bus would be arriving. He filed his first patent application in 1993.

Jones' BusCall business had trouble growing beyond a few clients. In demand letters, Jones' lawyers blame that on "widespread copying and infringement of his technologies." Jones "was thus left with no other way to protect his rights and 20+ years of hard work" except to file patent infringement lawsuits.

Many of the original Jones patents have expired, but the lawyers continue to assert US Patent No. 6,415,207, which is unexpired and has now been challenged by Unified.

In its IPR petition against Shipping & Transit, Unified Patents points to several other patents that predate the '207 patent, which was filed in 1999. One of those is another Jones patent, filed in 1995.

Earlier patents had all the elements of the '207 patent, which simply automates Caller ID systems and combines them with computer databases.

The EFF also filed a lawsuit against Shipping & Transit LLC in May, seeking to invalidate the '207 patent and two others. According to the EFF, the Jones patents have spawned "the most prolific patent troll in the country." Despite the fact that Shipping & Transit has filed more than 500 lawsuits, no judge or jury has ever weighed in on the merits of its patent claims.

The petition against Uniloc points out that DRM "had been a well-researched and widely implemented technology" well before the Uniloc patent was filed in 2007. Microsoft, IBM, and Hewlett-Packard all had established systems to control the number of people who could copy a purchased piece of software. Copy protection for Microsoft Windows XP began at least as early as 2001, as users of that product were required to enter a product ID and a hardware hash.

The petition against Sportbrain Holdings notes that "sensing units," including ones with memory storage, were used to collect sports data well before Sportbrain's inventor Henry Heslop filed his patent no. 7,454,002. Various portable monitors collected step data, gait activity, and a person's position and demonstrate that Heslop hadn't invented anything novel when he described a system that gave "processed feedback" to users. "There were many well-known, obvious solutions to these abstract problems," wrote lawyers for Unified Patents.

Correction: This story's headline originally said the petitions filed by Unified Patents challenged the top three non-practicing entities of 2015. In fact, the three targeted entities are the most litigious patent filers of the current year, 2016. The headline has been changed to reflect that.