- Bad actors installed the surveillance technology by phoning the target through WhatsApp's call functionality, according to the Financial Times, which first spotted the issue.
- The FT reported that the spyware was developed by Israel's NSO Group.
- WhatsApp is urging users to update the app after it was targeted by "an advanced cyber actor."
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WhatsApp was hacked and attackers installed sophisticated spyware on an unknown number of people's smartphones.
The Facebook subsidiary, which has 1.5 billion users, said "an advanced cyber actor" infected an unknown number of people's devices with the malware, which it said it discovered in early May.
The Financial Times first reported the vulnerability . It said the bad actors were able to install the surveillance technology by phoning the target through WhatsApp's call functionality.
The FT reported that the spyware was developed by Israel's NSO Group, whose Pegasus software is known to have been used against human rights activists. The firm denied any involvement in a statement to the FT.
"This attack has all the hallmarks of a private company known to work with governments to deliver spyware that reportedly takes over the functions of mobile phone operating systems," WhatsApp said in a statement to the FT.
"We have briefed a number of human rights organisations to share the information we can, and to work with them to notify civil society."
A notice on Facebook said the issue impacted both Android, iPhones, and Windows phones. An update was released on Monday that should resolve the issue and users are being urged to update , regardless of whether they have had any suspicious call activity.
Citing a source, the FT reported that the US Department of Justice was notified about the hack last month.
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