Open-source software leader Red Hat has filed a complaint against a Canadian company it says has launched “an aggressive litigation campaign” against four industry giants for allegedly violating patents by using open-source technologies.

The complaint, filed Monday in the U.S. District Court of the Northern District of California alleges VirtaMove Corp. is attempting to assert ownership of open-source software used by IBM, Hewlett Packard Enterprise, Google and Amazon.com Services. The four cases are pending in district courts in Texas.