WhatsApp spokesperson told NBC News the attack targeted a number of users including journalists and members of civil society “across over two dozen countries, particularly in Europe.”

The spokesperson further said that Paragon Solutions has used a vector, a method to illegally access a network, to target the users and that “the vector involved using groups and sending a malicious PDF file.”

The spokesperson said the company has “successfully disrupted this exploitation vector.”

Following the attempted attacks, WhatsApp reportedly sent a cease-and-desist letter to the company.

The spokesperson told NBC News that those believed to be affected have been notified through WhatsApp chat and have been provided information on how to protect themselves from spyware.

Experts told The Guardian that targeting was a “zero-click” attack, which means targets would not have had to click on any malicious links to be infected.

WhatsApp reportedly notified victims of the attack of alleged hacking.

Journalist Francesco Cancellato says he was targeted

Francesco Cancellato, the editor-in-chief of the Italian online newspaper Fanpage.it, wrote in an article published on his portal that he was one of the victims of the attack.

What did experts say?

John Scott-Railton, a senior researcher at Citizen Lab, told NBC News that a hack such as this one has the ability to “turn a telephone into a spy in your pocket.”

Natalia Krapiva, senior tech-legal counsel at the advocacy group Access Now, wrote on X: "WhatsApp sent a cease-and-desist letter to #Paragon following the spyware attack on the messaging platforms’ users."

"Great to see actions like these by platforms to protect their users’ privacy and security," she said.

Paragon Solutions did not comment on the issue so far.