In a Wednesday mea culpa, Reddit – the online chat board that got a little out of hand and became the sixth most-visited website on the internet – has admitted it was raided by hackers unknown.

For four days, specifically June 14 to June 18, miscreants managed to break into the website's cloud hosting and source-code repository accounts of several Reddit employees, despite their accounts being locked down with two-factor authentication via SMS. It looks at this stage as though a man-in-the-middle attack was used to snatch the SMS tokens, allowing the accounts to be taken over. The staffers' phones themselves weren't hacked, it is claimed.

"We learned that SMS-based authentication is not nearly as secure as we would hope, and the main attack was via SMS intercept," the Reddit team said in a statement on Wednesday. "We point this out to encourage everyone here to move to token-based 2FA."

El Reg also highly recommends hardware tokens for multi-factor authentication rather than SMSes. Text messages can, for example, be intercepted by scumbags hijacking phone accounts in so-called port-out scams, or through SS7 tricks, or through browser-based attacks, or potentially eavesdropped over the air.

US standards lab says SMS is no good for authentication READ MORE

In this instance, it is not known exactly how the login SMSes were grabbed – they could have been phished, after all.

The attackers managed to snaffle a backup database of information that was submitted to the site from its launch in 2005 until May 2007, including usernames, passwords (although these were salted and hashed), email addresses, and all content including public and private messages.

That sounds bad, however, there are mitigating factors. Reddit wasn't that big for the first year or so of operation, and the founders have admitted that many of the accounts were sock puppets intended to drive initial traffic. The loss of private messages may be more serious, although they are all over a decade old.

Reddit also said that some email digests sent out between June 3 and June 17 have been stolen, showing which safe-for-work subreddits some email addresses were following. Affected users will be contacted by the biz if they were caught up in the theft.

The statement also mentions that the Reddit source code, internal logs, configuration files, and other employee workspace files were accessed.

"In other news, we hired our very first Head of Security, and he started 2.5 months ago," said Reddit CTO Christopher Slowe. "I’m not going to out him in this thread for obvious reasons, and he has been put through his paces in his first few months. So far he hasn’t quit." ®