Early reaction from security experts was mixed, with some believing the hacker's claim, while others were dubious.

Last week, conjecture had focused on a state-sponsored attack, perhaps funded or conducted by the Iranian government, that hacked a certificate reseller affiliated with U.S.-based Comodo.

On March 23, Comodo acknowledged the attack, saying that eight days earlier, hackers had obtained nine bogus certificates for the log-on sites of Microsoft's Hotmail, Google's Gmail, the Internet phone and chat service Skype and Yahoo Mail. A certificate for Mozilla's Firefox add-on site was also acquired.

SSL certificates validate the legitimacy of a Web site to the browser, assuring users that they're connecting to the real site, and that the traffic between their browsers and the site is encrypted.

Comodo CEO Melih Abdulhayoglu said last week that circumstantial evidence pointed to a state-backed attack, and claimed the . "We believe these are politically motivated, state driven/funded attacks," said Abdulhayoglu.