By Richard Chirgwin
Aussie cops grab journo for reporting Facebook vuln demo
A tech writer attending the AusCERT conference in Queensland says he has been arrested and released by Queensland Police over a story written at the conference.
Ben Grubb, a journalist for the Fairfax stable of newspapers, flicked off a short Tweet after his arrest: “I’ve been arrested by Queensland Police for a story I wrote today. They’ve also seized my iPad.” Later, other attendees of the conference said Grubb had been released and had returned to the conference.
His questioning apparently relates to this story, in which he detailed a demonstration by independent security researcher Christian Heinrich of Facebook vulnerabilities. Heinrich accessed privacy-protected photographs of the wife of HackLabs director Chris Gatford.
Grubb, writing for the Sydney Morning Herald, said Heinrich’s presentation claimed his attack worked not directly through Facebook, but through the content delivery network (CDN) Facebook uses for improved performance.
The vulnerability comes through the time-honoured practice of URL guessing, often mislabelled as a “hack”. In Heinrich’s case, the challenge was to guess the URL that the CDN attaches to privacy-protected photos.
To do this, he combined a Facebook friend ID with a brute-force-guess for the remainder of the URL to the photographs, in a process which Heinrich said meant testing 200,000 numerals and took around seven days.
The mystery is why Grubb was singled out from the conference attendees, since they’re presumably in possession of the same information as anybody else who has viewed the Heinrich presentation.
Queensland Police have said Grubb wasn’t arrested, but questioned. Its media unit also said the iPad would be returned as soon as possible.
Update: Early on Wednesday morning (May 18), the Queensland Police Media Unit said its earlier statements were in error. It tweeted that “@bengrubb was arrested for questioning briefly. Our tweet last night was based on information provided at the time. Apologies.”