"Ex Parte Reexamination At any time during a patent’s enforcement period, a third-party may file for Ex Parte Reexamination. They may do so anonymously. The pe

"Ex Parte Reexamination At any time during a patent’s enforcement period, a third-party may file for Ex Parte Reexamination. They may do so anonymously. The petitioner must provide prior art to show a substantial and new question of patentability that was not previously considered in reviews of the patent. This standard is intended to prevent third-parties from raising frivolous challenges to patents. Reexamination is significantly different than Post-Grant Review and Inter Partes Review, because the proceeding is only between the patent owner and the USPTO. The petitioner usually does not play a role other than the initial filing. The review is conducted by a special panel of examiners called the Central Reexamination Unit (CRU) and usually takes two years. A patent owner may appeal a decision by the CRU to the PTAB and then the U.S. Court of Appeals. Ex Parte Reexamination might be attractive to third-parties that have strong prior art to challenge a patent and want to remain anonymous. It is also relatively cheap for the petitioner because they are not involved in the proceedings." https://entrepreneurship.law.umich.edu/challenging-patent-validity-at-the-uspto/ https://entrepreneurship.law.umich.edu/challenging-patent-va...