...investigators set up a secure lab to examine the phone and its artifacts and spent two days poring over the device but were unable to find any malware on it. Instead, they only found a suspicious video file sent to Bezos on May 1, 2018 that "appears to be an Arabic language promotional film about telecommunications."
That file shows an image of the Saudi Arabian flag and Swedish flags and arrived with an encrypted downloader. Because the downloader was encrypted this delayed or further prevented "study of the code delivered along with the video."
Investigators determined the video or downloader were suspicious only because Bezos' phone subsequently began transmitting large amounts of data. "[W]ithin hours of the encrypted downloader being received, a massive and unauthorized exfiltration of data from Bezos' phone began, continuing and escalating for months thereafter," the report states.
"The amount of data being transmitted out of Bezos' phone changed dramatically after receiving the WhatsApp video file and never returned to baseline. Following execution of the encrypted downloader sent from MBS' account, egress on the device immediately jumped by approximately 29,000 percent," it notes. "Forensic artifacts show that in the six (6) months prior to receiving the WhatsApp video, Bezos' phone had an average of 430KB of egress per day, fairly typical of an iPhone. Within hours of the WhatsApp video, egress jumped to 126MB. The phone maintained an unusually high average of 101MB of egress data per day for months thereafter, including many massive and highly atypical spikes of egress data."
The Motherboard article also quotes forensic experts on the report:
A mobile forensic expert told Motherboard that the investigation as depicted in the report is significantly incomplete and would only have provided the investigators with about 50 percent of what they needed, especially if this is a nation-state attack. She says the iTunes backup and other extractions they did would get them only messages, photo files, contacts and other files that the user is interested in saving from their applications, but not the core files.
"They would need to use a tool like Graykey or Cellebrite Premium or do a jailbreak to get a look at the full file system. That's where that state-sponsored malware is going to be found. Good state-sponsored malware should never show up in a backup," said Sarah Edwards, an author and teacher of mobile forensics for the SANS Institute.
"The full file system is getting into the device and getting every single file on there -- the whole operating system, the application data, the databases that will not be backed up. So really the in-depth analysis should be done on that full file system, for this level of investigation anyway. I would have insisted on that right from the start."
The investigators do note on the last page of their report that they need to jailbreak Bezos's phone to examine the root file system. Edwards said this would indeed get them everything they would need to search for persistent spyware like the kind created and sold by the NSO Group. But the report doesn't indicate if that did get done.