Enlarge / A wall of user photos form a Facebook logo at the company’s data center in Lulea, Sweden. The switches used in Facebook’s data centers are one of several products accused of infringing two patents that originated with 3Com but are now owned by a patent-licensing company. (credit: JONATHAN NACKSTRAND/AFP/Getty Images)

Patents that only recently were in the hands of Hewlett Packard Enterprise were used last week to sue several companies that build switches and routers, including Cisco (PDF), Juniper Networks (PDF), and Facebook (PDF). A recently created shell company called Plectrum LLC filed the lawsuits in the Eastern District of Texas, a remote judicial district that continues to be a hotspot for patent cases.

The lawsuits are remarkable in part because Hewlett Packard is a company that only recently prided itself on not allowing its patents to be used for offensive purposes, even if they got sold. That attitude started changing about five years ago. Patent office records show that HP transferred the two patents in these lawsuits to Plectrum in September. On Thursday, Plectrum sued Cisco, Brocade, Fortinet, Huawei, Facebook, Extreme Networks, Arista Networks, and Juniper Networks.

The two patents used in the lawsuits originated at the 3Com Corporation, which was bought by HP in 2010, along with about 1,400 patents. US Patent No. 6,205,149 is entitled “Quality of service control mechanism and apparatus,” while US Patent No. 5,978,951 describes the use of a “high speed cache management unit” which replaces some software-based systems with hardware in order to reduce latency time.