Eric Grosse, engineering director for Google's security team, said in a blog post that hundreds of users have been affected, including senor U.S. government officials, Chinese political activists, officials in several Asian countries such as South Korea, military personnel, and journalists.
"The goal of this effort seems to have been to monitor the contents of these users' emails, with the perpetrators apparently using stolen passwords to change peoples' forwarding and delegation settings," Grosse said.
By changing these settings, which are only evident through the appropriate Gmail Settings tab page, the attackers could generate copies of incoming and outgoing email that would be forwarded without the account holder's knowledge.
Google declined to provide further details or information about those it believes may be behind the attack.
In January 2010, Google reported that it had uncovered "a highly sophisticated and targeted attack on our corporate infrastructure originating from China." Google said at the time that it had reason to believe that one of the main goals of the attackers was to compromise the Gmail accounts of Chinese human rights activists.
In that respect, the attack was not very successful: While Google acknowledged that the attackers had stolen unspecified intellectual property, it stressed that only two Gmail accounts appeared to have been accessed.
An October 2009 report on Chinese cyber espionage prepared by defense contractor Northrop Grumman said that the Chinese military maintains at least six technical reconnaissance bureaus for gathering cyber intelligence in the Lanzhou, Jinan, Chengdu, Guangzhou, and Beijing military regions.
The current attack differs from the 2010 attack in that it doesn't involve a vulnerability in Google's infrastructure; it is simply a phishing campaign to dupe users into revealing their Gmail login credentials.
Google said that it detected the phishing campaign through its cloud-based security and abuse detection systems, through the reports from users, and through a report published in February on the Contagio blog, a collection of malware samples and threat analysis. The company said it has notified victims and the relevant government authorities.
Google is advising Gmail users to consider steps to improve the security of their accounts. The company recommends using two-factor verification, using a strong password, only entering account information at the proper Google domain, checking Gmail settings for unknown forwarding addresses or unauthorized account delegation, watching for suspicious account activity warnings, using Google Chrome, and reviewing security education materials available online.
In this new Tech Center report, we profile five database breaches--and extract the lessons to be learned from each. Plus: A rundown of six technologies to reduce your risk. Download it here (registration required).