The company said that thousands of its users inside Iran had been the targets of a sophisticated email phishing campaign in which attackers sent users a link that, when clicked, sent them to a fake Google sign-in page where the attackers could steal login credentials.

Google would not say how it had traced the spy campaign to Iran because it did not want to tip off attackers. It did say, however, that it was confident the attackers were the same ones behind a sophisticated attack in 2011 on DigiNotar, a Dutch company that sells certificates that validate the security of a website. By compromising the certificate authority, the attackers were able to intercept users' Web traffic and compromise their computers.

Security researchers who analysed the DigiNotar attack believe the company was compromised by Iran or hackers working on its behalf. By tying the latest Iranian phishing campaign to Iran, Google's findings Wednesday seemed to confirm that Iran was also behind the DigiNotar attack.

Of the DigiNotar attack, Phil Zimmermann, a pioneer of encryption software said, "There are thousands of Iranian dissidents in prison today because of that."

Compared with the public uproar that followed Iran's 2009 elections, the run-up to this week's elections has been tightly controlled. Many leaders of the 2009 opposition have fled the country, been silenced or jailed. The two main presidential challengers in those elections, Mir Hossein Mousavi and Mahdi Karroubi, remain under house arrest.
New York Times