Reddit breach exposes non-critical user data

Reddit announced today that it suffered a security breach in June that exposed some of its internal systems to the attackers, although what was accessed was not particularly sensitive. Notably the hack was accomplished by circumventing the two-factor authentication Reddit had in place via SMS interception — which should be a wake-up call to any who haven’t moved on from that method.

A post by Reddit CTO Chris Slowe (as KeyserSosa, naturally) explained that they discovered the hack on June 19, and estimated it to have taken place between June 14 and 18. The attack “compromised a few of our employees’ accounts with our cloud and source code hosting providers,” he wrote, gaining “read-only access to some systems that contained backup data, source code and other logs.”

Said access was gated behind two-factor authentication systems, but unfortunately they were of the type that occasionally or optionally allow SMS to be used instead of an authenticator app or token. SMS has some major inherent security flaws, and this method was declared unacceptable by NIST back in 2016. But it is far from eliminated, and many services still use it as a main or backup 2FA method.

Reddit itself, it is worth noting, only provides 2FA via token. But at least one provider of theirs didn’t, it turns out, and the attackers took advantage of that. (Slowe said they know no phones were hacked, which suggests the SMS authentication codes were intercepted otherwise, possibly via spoofing a phone or scamming the provider.)

Although a complete inventory of what was accessed by the hackers isn’t made available, Slowe said that there were two main areas of concern as far as users were concerned:

  • A complete copy of Reddit data from 2007, comprising the first two years of the site’s operations. This includes usernames, salted/hashed passwords, emails, public posts and private messages.
  • June’s email digests, with usernames and associated emails.

Reddit is a different and much, much bigger place today than it was in 2007; anyone who remembers the big migration from Digg in those days will also remember how small and limited it was.

Still, these data together could still be useful to malicious actors looking to scam people on this list — if I were them, I’d be sending fake email digests asking them to log in, or building a list of username-email pairs and matching those to other sites. And of course you might want to, as Slowe put it, “think about whether there’s anything on your Reddit account that you wouldn’t want associated back to that address.”

If you’re one of the people affected, you should be receiving an email or PM that should inform you of your risk — for example, if your password hasn’t been changed since 2007, which would be its own security risk. I joined in July 2007 and haven’t received either, as a data point.

Slowe also noted that the company has alerted the appropriate authorities as required and has improved security since the event.