I hate hyperbolic news headlines about data breaches, but for the "2 Billion Email Addresses" headline to be hyperbolic, it'd need to be exaggerated or overstated - and it isn't. It's rounded up from the more precise number of 1,957,476,021 unique email addresses, but other than that, it's exactly what it sounds like. Oh - and 1.3 billion unique passwords, 625 million of which we'd never seen before either. It's the most extensive corpus of data we've ever processed, by a significant margin.
A couple of weeks ago, I wrote about the 183M unique email addresses that Synthient had indexed in their threat intelligence platform and then shared with us. I explained that this was only part of the corpus of data they'd indexed, and that it didn't include the credential stuffing records. Stealer log data is obtained by malware running on infected machines. In contrast, credential stuffing lists usually originate from other data breaches where email addresses and passwords are exposed. They're then bundled up, sold, redistributed, and ultimately used to log in to victims' accounts. Not just the accounts they were initially breached from, either, because people reuse the same password over and over again, the data from one breach is frequently usable on completely unrelated sites. A breach of a forum to comment on cats often exposes data that can then be used to log in to the victim's shopping, social media and even email accounts. In that regard, credential stuffing data becomes "the keys to the castle".