Gmail, Hotmail and Yahoo Mail users have become a victim of another hack by Russia's criminal underworld, exposing their usernames and passwords to other people online.

According to security expert Alex Holden of Hold Security, a huge data breach consisting of some 273.3 million online accounts has been exposed. The data breach contains 57 million accounts. Russia's own Mail.ru email service accounts for the majority of hacked accounts, but a large number also belong to Gmail, Hotmail and Yahoo Mail users. Yahoo Mail credentials totalled 40 million, Hotmail accounted for 33 million, while 24 million belonged to Gmail account holder.

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The data breach does not only contain email accounts but also thousands of other stolen username and password combinations that appear to belong to employees of some of the largest American banking, manufacturing and retail companies.

These stolen accounts were discovered by Hold Security, where researchers found a Russian hacker called “The Collector,” bragging that he was ready to give away the credentials. He was asking for just 50 rubles or less than $1 for the data, but Holden was given the information for free after he agreed to post positive comments about the Russian in various hacker forums.

“This information is potent. It is floating around in the underground and this person has shown he’s willing to give the data away to people who are nice to him. These credentials can be abused multiple times,” said Alex Holden, founder and chief information security officer at Hold Security.

The Russian email provider’s initial checks found no live combinations of user names and passwords that match existing emails. Currently, Microsoft, Google and Yahoo are all investigating the leaked data and talking with Hold Security.

It is also worth noting that while tens of millions of Gmail, Yahoo and Hotmail accounts were affected, the total percentage of accounts compromised compared to the total in circulation is relatively small.

TagsRussian Hacker, hacker, Gmail, Hotmail, Yahoo, Gmail hack, username password hack, Data breach, username leak, password leak