Hundreds of millions of usernames and passwords belonging to Gmail, Hotmail and Yahoo Mail are being traded among Russia’s underworld.

Alex Holden, founder and chief information security officer of Hold Security, claims to have uncovered the largest data breach to date, publishing details of 272.3 million stolen accounts being traded.

Russia’s own Mail.ru e-mail service accounts for the majority of hacked accounts at 57 million, but a large number also belong to Gmail, Hotmail and Yahoo Mail users.

Yahoo Mail credentials totalled 40 million, or 15 percent of the haul, while Hotmail accounted for 33 million, or 12 percent, and 24 million, or nine percent, belonged to Gmail account holders.