Snowden further explained on Twitter: "The global technological consensus is against the FBI," he wrote — linking to a blog post on the American Civil Liberties Union website explaining exactly how the FBI could have bypassed the iPhone's auto-erase function on its own. That's "one example," he wrote.
Other technologists have explained how the FBI could have easily accessed the phone's latest iCloud backup if agents working with San Bernardino County had not reset the iCloud password. The county owns the phone used by Farook.
Even so, security researchers say there are other options, like "de-capping" the phone's memory chip to access it outside the phone (which Snowden has also mentioned), or resetting the phone's internal counter so that you can guess the passwords as many times as you want. Those techniques are hard and expensive and could destroy the phone, experts say — but have worked in the past.