The US government is stepping up its investigation into Israeli firm NSO Group, according to recent reports that lawyers with the Department of Justice recently requested more information regarding a current legal battle between NSO Group and WhatsApp, a popular messaging platform. NSO Group creates controversial spyware and is accused of being responsible for cyberespionage attacks using the malicious Pegasus spyware on 1400 WhatsApp users.

WhatsApp claims that the attackers used servers and internet hosting services associated with NSO Group, claiming they believe they were responsible for the attacks which targeted political dissidents, senior government officials, human rights activists, and journalists. Most of the victims were located in the United Arab Emirates, Mexico, and Bahrain, according to Facebook. It is unclear how far along the investigation is. NSO Group claims that its products are only sold to law enforcement agencies and governments. Last year, Microsoft, Google, Cisco, and other big-name tech giants filed an amicus brief in support of Facebook’s position in the legal battle against the Israeli firm.

Read More: DoJ Steps Up Investigation into NSO Group