Unknown attackers installed spyware on mobile phones using the call feature in the WhatsApp app, Financial Times reported.

According to this source, the attackers introduced spyware, making calls to selected phone numbers through the WhatsApp app. At the same time, the malicious code was downloaded, even if the subscriber did not pick up the phone, and the call information was deleted from the phone’s memory. It is noted that the devices on iOS and Android platforms were vulnerable to attack.

One of the victims of the cyber attack was a famous British lawyer and human rights activist, his name was not disclosed. WhatsApp found out about the problem in early May, last week the company reported it to the US Department of Justice.

According to the Financial Times, the developer of the tracking program is the Israeli private company NSO Group, engaged in the production of cyber intelligence tools. The company said they are investigating the WhatsApp incident. At the same time, NSO Group noted that the company itself does not use its developments, and the software is managed exclusively by those who buy its technology.

According to the Sky News channel, WhatsApp confirmed the cyber attack, noting that it was limited in scope and affected only a few dozen users. The company also informed that the vulnerability that allowed installing the tracking software was eliminated, and also recommended that users update their apps version.

The WhatsApp audience currently stands at 1.5 billion people worldwide, FT added.