A US appeals court ruled that Facebook can pursue a case accusing Israel’s NSO Group of exploiting a weakness in its WhatsApp messaging programme to install malware that allowed 1,400 people, including journalists, human rights activists, and dissidents, to be monitored.

The 9th US Circuit Court of Appeals in San Francisco rejected privately owned NSO’s contention that it was exempt from suit because it had operated as a foreign government agent in a 3-0 judgement on Monday.

In October 2019, Facebook, now known as Meta Platforms Inc, sued NSO for an injunction and damages, accusing it of illegally accessing WhatsApp servers six months prior to install its Pegasus virus on victims’ phones.

Pegasus, according to NSO, aids law enforcement and intelligence organisations in combating crime and protecting national security.

It was challenging a trial judge’s refusal in July 2020 to grant it “conduct-based immunity,” which is a common law provision that protects foreign officials working in their official capacity.

Circuit Judge Danielle Forrest upheld the verdict, saying it was a “easy case” since NSO’s mere licencing of Pegasus and provision of technical support did not protect it from accountability under federal law, which preempted common law.

“Whatever NSO`s government customers do with its technology and services does not render NSO an `agency or instrumentality of a foreign state,`” Forrest wrote. “Thus, NSO is not entitled to the protection of foreign sovereign immunity.”

Judge Phyllis Hamilton of the United States District Court for the Northern District of California will hear the case again.

In an email, NSO stated that its technology aids in the public’s defence against severe crime and terrorism, and that it “remains undeterred in its objective.”

The judgement, according to WhatsApp spokesman Joshua Breckman, is “an crucial step in holding NSO accountable for its attacks against journalists, human rights defenders, and government authorities.”

Microsoft Corp, Alphabet Inc’s Google, and Cisco Systems Corp all backed Facebook’s case, calling surveillance technologies like Pegasus “potent and dangerous” in a court declaration.

The US government put NSO and Israel’s Candiru on a no-fly list on Nov. 3 for allegedly delivering spyware to governments that used it to “maliciously target” journalists, activists, and others.

WhatsApp Inc et al v NSO Group Technologies Ltd et al, No. 20-16408, 9th U.S. Circuit Court of Appeals