A Linux group is hoping to discredit three Microsoft patents that were at the heart of a recent lawsuit with GPS device maker TomTom.

The Open Innovation Network is asking people to examine three patents and submit any so-called "prior art" that might call into question the validity of the patents.

Prior art is information published before the patent was issued that describes similar technology.

The patents were at the heart of a lawsuit Microsoft filed against TomTom. As part of a settlement, TomTom agreed to pay Microsoft to license the patents for technologies in its car navigation and file management system.

The settlement worried the Linux community because the patents involve technologies found in the Linux OS that TomTom uses in its portable devices.

While Microsoft has recently seemed to ease up on its threats against Linux, it has in the past claimed that Linux violates hundreds of its patents.

The TomTom dispute raised fears that Microsoft might pursue other companies using similar technology or start more aggressive action against other Linux users too.

Microsoft said it believes the patents are strong enough to withstand scrutiny. Two have each been affirmed twice by the U.S. Patent and Trademark Office and have been licensed to 18 other companies, said Horacio Guiterrez, deputy general counsel at Microsoft, in a statement.

All three "have been validated through licensing agreements and highly scrutinized for validity by patent offices," he said.

At the time it filed the suit against TomTom, Microsoft said open source was not the focal point of its complaint. The case was about TomTom's specific implementation of the Linux kernel, Microsoft said.

The Open Innovation Network has posted the patents relevant to the TomTom issue online and invited anyone to submit information about the patents on the site.

TomTom declined to comment on the Open Innovation Network campaign.