Cybercrooks are offering to sell "stolen copies" of the leaked eBay database through an advert posted through Pastebin.
However eBay says the sale is fake. "We have checked all published data and so far none are authentic eBay accounts," eBay's press office told El Reg.
Security experts, although far from certain, seem inclined to agree.
The dodgy seller is offering to sell the "full eBay database dump" with 145 million records on a non-exclusive basis for 1.453 BTC (or $750).
A sample lump purporting to contain the compromised details of more than 12,000 users from the APAC region has been uploaded through Mega. The validity of the data on sale is unverified.
The Mega sample contains name, email address and postal addresses. Passwords are hashed and not revealed.
Security expert Kenn White reported finding several of the leaked email addresses in existing dumps. Other security experts are also wary.
"It’s not yet been verified that these are legitimately eBay credentials, and it’s possible that a criminal has just spotted an opportunity to cash in on the attack with some other credentials dump they have," said Trey Ford, global security strategist at Rapid7.
"That said, during initial analysis of 12,663 of the records which have been provided as a free sample, we were able to find some matches between email prefixes and eBay profile name where people are using the same handle."
“This doesn't necessarily mean these credentials are from the eBay attack – it could be that people use the same handle across multiple sites including one that was previously compromised, and the creds are actually from that. In fact, we also found matches between these email addresses and a popular Malaysian web forum, which may point to the true source of these credentials. We have no way to confirm how statistically representative the leaked APAC sample is of the broader eBay dataset," he added.
If genuine the leaks were hashed using a strong algorithm and attempts to find hashes corresponding with the simplest passwords have failed to come up with anything, which is in itself suspicious.
The credentials set is using PBKDF2 (Password-Based Key Derivation Function 2) SHA-256 hashes. "This means they employ a strong hash function and also intentionally make cracking them more difficult and slow by individually salting and using a high number of hash iterations," Ford explained.
Security consultant Per Thorsheim is also skeptical. "PBKDF2 with 12K iterations takes a looooong time to crack. No hashes cracked yet, 123456 should have been found among 12K," he said in a Twitter update. "it looks like we call FAKE on the @KbcdPfA alleged eBay leak up for sale." ®