A computer hacker has leaked a list of names, addresses and telephone numbers it claims belong to Visa and Mastercard customers.
In a series of posts on the social networking site Twitter, the hacker who goes by the name of Reckz0r - claims to have infiltrated both companies' systems and acquired their data.
"Guess what folks? Mastercard and Visa are pwned," the hacker wrote. "Don't believe me? Keep your patience, I'll provide a lovely demo for you soon."
The hacker then told followers to expect a "data dump" of the acquired information yesterday.
Since then, Reckz0r has posted a link to a file on the text sharing website Pastebin, which contains contact details of several hundred people from the United States, Australia and the UK.
"I just leaked a half data of Visa and Mastercard, the full one is about 50GB or bigger," the hacker added.
In a statement to IT Pro, Mastercard declined to confirm or deny the authenticity of the data, adding that it doesn't comment on "rumours, threats or speculation."
Meanwhile, in a further statement to IT Pro, Visa confirmed that it was investigating the breach.
"Visa Europe takes data compromise very seriously," said the company. "Working closely with partners, including law enforcement, we are investigating this allegation."
