Whatsapp urges users to update app after attacked by advanced spyware via missed calls

Facebook's WhatsApp have urged users to update their app immediately, after it was hit by one of the worst security bugs ever seen.

The flaw allows the app to be attacked through a missed call – and until the update was released there was nothing an affected user could do.

Once hit, the phone would be compromised without the user knowing.

A WhatsApp spokesman said the attack had "all the hallmarks of a private company that has been known to work with governments to deliver spyware that has the ability to take over mobile phone operating systems."

"WhatsApp encourages people to upgrade to the latest version of our app, as well as keep their mobile operating system up to date, to protect against potential targeted exploits designed to compromise information stored on mobile devices," a spokesman said.

"We are constantly working alongside industry partners to provide the latest security enhancements to help protect our users," he said.

The spyware was able to be transmitted when attackers called a target's device, irrespective of whether or not they answered the call.

Logs of incoming calls were also erased, according to the Financial Times, which first reported the breach.

An update is now available for all major platforms that fixes the bug, and security experts have urged users to ensure that their phones are up to date as soon as they can.