SAN FRANCISCO/NICOSIA, Cyprus (REUTERS, AFP) – Tech giants including Microsoft and Google on Monday (Dec 21) joined Facebook’s legal battle against hacking company NSO, filing an amicus brief in federal court that warned that the Israeli firm’s tools were “powerful, and dangerous.”

The brief, filed before the US Court of Appeals for the Ninth Circuit, opens up a new front in Facebook’s lawsuit against NSO, which it filed last year after it was revealed that the cyber surveillance firm had exploited a bug in Facebook-owned instant messaging programme WhatsApp to help surveil more than 1,400 people worldwide.