Google is directly contacting users in Iran, who may have been compromised by a rogue SSL certificate, to recommend measures to secure their accounts.
While Google's internal systems were not compromised, it is directly contacting possibly affected users and providing information on securing their accounts because its top priority is to protect the privacy and security of its users, said Eric Grosse, vice president of security engineering.
Close to 300,000 unique IP addresses from Iran requested access to google.com using a rogue certificate issued by Dutch digital certificate authority DigiNotar, between August 4 and August 29, according to an interim report by security firm, Fox-IT.
The list of IP addresses would be handed over to Google who can inform users that their email may have been intercepted during this period, Fox-IT said.
Google said last week it received reports of attempted SSL (secure sockets layer) man-in-the-middle attacks against Google users, whereby someone tried to get between them and encrypted Google services. The attacker used a fraudulent SSL certificate issued by DigiNotar, affecting primarily people located in Iran.
Google Chrome users were protected from the attack because Chrome was able to detect the fraudulent certificate, Google said last week. The company advised all users in Iran to take steps to secure their accounts.
The compromise of DigiNotar could have put the Internet communications of many Iranians at risk, including their Gmail, it said.
Users have been advised to change their Google account passwords, verify account recovery options, and to check the websites and applications that are allowed to access their account, and revoke any that are unfamiliar.
Google has also provided web links to where users can check their Gmail settings for suspicious forwarding addresses or delegated accounts. Users are also advised to pay attention to warnings that appear in their web browser and not click past them.
A total of 531 fraudulent digital certificates were issued by DigiNotar for domains that included google.com, the CIA and Israel's Mossad. The list of domains and the fact that 99 percent of the users are in Iran suggest that the objective of the hackers was to intercept private communications in Iran, Fox-IT said.
A hacker styling himself as Comodohacker claimed on Pastebin that he breached DigiNotar in order to punish the Dutch government for the actions of its soldiers in Srebrenica, where 8,000 Muslims were killed by Serbian forces in 1995 during the Bosnian War.
He used the same Pastebin account that was used earlier this year to describe the attack on Comodo, which issues SSL certificates. Comodohacker said he had penetrated the networks of StartCom, a certificate authority in Israel, and GlobalSign in the US.