An attack that stole user credentials of over 8,000 Tumblr users has been detected and named as one of 'the largest and most successful phishing attacks of its kind to date'.

Christopher Boyd, senior threat researcher at GFI Software, first noticed the attack on 23rd June when users of the content-sharing website were asked to take a test to become a member of the 'Tumblr IQ Society'. He said that this morphed into a high-yield phishing campaign that has propagated across the Tumblr platform and managed to steal thousands of credentials.

He said that the Tumblr IQ domain was registered on the 15th June and the adverts began on the 23rd promoting the 'Tumblr IQ Society'. Shortly after, additional domains started to appear and then compromised accounts appeared, serving up a mixture of Tumblr hosted text and login credential submission forms served up by free web hosting accounts.

Boyd said that while many of the compromised Tumblr accounts wanted users to login on the same page, many more were redirecting end-users to a fake Tumblr login website.

Boyd said: “If ever a scam page had a name that implied you should do the exact opposite of what it suggested, it would be that one. The problem has become so pervasive that regular Tumblr users are setting up dedicated anti-phishing sites to advise users of the problem. One of these sites actually pointed us in the direction of one of the drop zones used for the stolen logins and the problem does indeed seem to be out of control at this point.

“The data we saw contained 8,200 lines of text stretched across 304 pages of Microsoft Word and even accounting for the inevitable duplicates and fake data, that's still quite the goldmine of pilfered login credentials.”

He later said that all three domains were not available but they could well return at some point and he recommended Tumblr users to verse themselves in the art of phishing scams.

“The end game for all of this user data is still unknown, but recent data breaches indicate the attackers could seek to take advantage of password reuse across multiple sites and services, potentially breaking into emails, social network accounts and banking services for personal gain. Tumblr are aiding users who have contacted them in relation to potentially phished accounts, and have been notified in relation to the compromised data,” said Boyd.