The spyware, developed by Israeli cyber intelligence company, used infected phone calls to take over the functions of operating systems

WhatsApp is encouraging users to update to the latest version of the app after discovering a vulnerability that allowed spyware to be injected into a user’s phone through the app’s phone call function.

The spyware was developed by the Israeli cyber intelligence company NSO Group, according to the Financial Times, which first reported the vulnerability.

Attackers could transmit the malicious code to a target’s device by calling the user and infecting the call whether or not the recipient answered the call. Logs of the incoming calls were often erased, according to the report.

WhatsApp said that the vulnerability was discovered this month, and that the company quickly addressed the problem within its own infrastructure. An update to the app was published on Monday, and the company is encouraging users to upgrade out of an abundance of caution.

WhatsApp 'deleting 2m accounts a month' to stop fake news Read more

The company has also alerted US law enforcement to the exploit, and published a “CVE notice”, an advisory to other cybersecurity experts alerting them to “common vulnerabilities and exposures”.

The vulnerability was used in an attempted attack on the phone of a UK-based attorney on 12 May, the FT reported. The lawyer, who was not identified by name, is involved in a lawsuit against NSO brought by a group of Mexican journalists, government critics and a Saudi Arabian dissident.

“The attack has all the hallmarks of a private company reportedly that works with governments to deliver spyware that takes over the functions of mobile phone operating systems,” WhatsApp said in a statement. “We have briefed a number of human rights organizations to share the information we can and to work with them to notify civil society.”

NSO Group did not immediately respond to the Guardian’s request for a comment. The company told the FT that it was investigating the WhatsApp attacks.

Q&A WhatsApp hack: what should I do? Show Hide Users are strongly advised to check for WhatsApp updates manually through the Apple App Store on an iPhone, Google Play or similar on an Android device, the Microsoft Store on Windows Phones and the Galaxy app store on Tizen devices. A vulnerability in the popular Facebook-owned messaging service has been discovered that allowed hackers to install spyware through an infected WhatsApp voice call. The spyware is capable of trawling through calls, texts and other data, activating the phone’s camera and microphone and performing other malicious activities. All brands of phones with WhatsApp or WhatsApp Business installed are affected, including Apple’s iPhone (iOS), Android phones, Windows Phones and Tizen devices, according to Facebook. WhatsApp is used by 1.5 billion people globally. Facebook implemented a server-side change to help protect users and pushed out updates for the various smartphone WhatsApp versions on Monday. Samuel Gibbs

“Under no circumstances would NSO be involved in the operating or identifying of targets of its technology, which is solely operated by intelligence and law enforcement agencies,” NSO Group told the FT. “NSO would not, or could not, use its technology in its own right to target any person or organization, including this individual.”

NSO limits sales of its spyware, Pegasus, to state intelligence agencies. The spyware’s capabilities are near absolute. Once installed on a phone, the software can extract all of the data that’s already on the device (text messages, contacts, GPS location, email, browser history, etc) in addition to creating new data by using the phone’s microphone and camera to record the user’s surroundings and ambient sounds, according to a 2016 report by the New York Times.

WhatsApp has about 1.5bn users around the world. The messaging app uses end-to-end encryption, making it popular and secure for activists and dissidents. The Pegasus spyware does not affect or involve the app’s encryption.