Facebook has blamed Apple's operating system for the hacking of Amazon Founder and CEO Jeff Bezos' phone, saying WhatsApp's end-to-end encryption is unhackable.

Investigators believe that Bezos's iPhone was compromised after he received a 4.4MB video file containing malware via WhatsApp - in the same way when phones of 1,400 select journalists and human rights activists were broken into by Pegasus software from Israel-based NSO Group last year.