Washington scrambled on Thursday to assess whether security had been compromised after Google Inc revealed a major hacker attack targeting US officials that the Internet giant pegged to China.
"These allegations are very serious," US Secretary of State Hillary Clinton said.
"We take them seriously; we're looking into them," Clinton told reporters a day after the Internet giant said it had disrupted a campaign aimed at stealing passwords of hundreds of Google email account holders, including senior US government officials, Chinese activists and journalists.
Google's announcement fuels debate in Washington over China's intentions in cyberspace, which the United States has identified as a potential flashpoint for future conflict.
Neither Google nor the US government has said that the Chinese government was behind the attacks, and the US state department said that it had not raised the issue with Beijing.
Google only said that the attack appeared to originate in China.
Beijing nevertheless reacted angrily to Google's charge, saying it was "unacceptable" to blame Beijing and allegations that China supports hacking "have ulterior motives".
Clinton said that Google told the state department before it made its public announcement on Wednesday, and the US FBI was investigating, with Google.
The White House said that it had no reason to believe official government e-mails were hacked in the Google incident, and officials at many agencies stressed that government employees were directed not to use private accounts to discuss sensitive issues.
"Rule number one is: don't do anything stupid," one national security official said.
Some government agencies, including the Securities and Exchange Commission and the Commodity Futures Trading Commission, block employees from accessing personal accounts from work. But there is no blanket ban and other agencies do allow it.
Still, the government will check whether senior officials' private accounts were targeted, officials said.
"I don't believe we're aware that anyone was affected in this building," state department spokesman Mark Toner said. "We'll continue to look into the possibility that some individuals here may have been affected."
While Google stressed that the hacking revelations did not reflect a security problem with its email service, analysts said competitors Blackberry maker Research In Motion and Microsoft Corp. could get a boost from the hacking incident.
The companies have been fending off competitive challenges from Google's Android software and cloud computing services, as the corporate sector and the federal government explore whether Google is a secure alternative for email.
"I would think this is a negative for Google in getting Android into federal government, but a bigger negative for Google's efforts to get federal government to use their cloud-based apps like Gmail and Google Docs," said Tavis McCourt, an analyst from Morgan Keegan.
Dueling in cyberspace
Google's latest salvo looked likely to bring Internet policy to the foreground in the US-China relationship, where Washington and Beijing have staked out sharply contrasting approaches to censorship, freedom of speech and cybersecurity.
The United States was drawn in last year when Google temporarily shut its Chinese-language portal over censorship concerns and a cyber attack it said was traced to China. Clinton also has accused Beijing of facing a "dictator's dilemma" as it seeks to control technologies that are fueling growth and free speech around the world.
The dispute over the Internet has at times amplified existing strains in the US-China relationship on everything from human rights and trade to intellectual property rights.
The latest Google hacking attempt follows a series of high-profile hacking cases that have hit US defense giant Lockheed Martin, entertainment giant Sony and others. A US official familiar with progress on the investigation said that there was increasing suspicion the Lockheed hack originated with "someone in China."
China, often the first to be blamed, says it is being unfairly accused by countries that are simply unhappy at how Chinese growth is swiftly eroding Western economic, military and geopolitical dominance.
The United States has warned that a devastating cyberattack could result in real-world military retaliation, although analysts say it could be difficult to detect its origin with full accuracy.
"Folks tend to tie a lot of the hacking activity to China, but ... my sense is that you're moving into a realm (where) you can't always say it's a state actor," Chief of Naval Operations Admiral Gary Roughead told Reuters in an interview.
The White House and the state department have appointed officials to oversee cybersecurity issues. The Pentagon probably has the most developed strategy in the US government, with a Cyber Command and thousands of people in different divisions of the military dedicated to matters of cybersecurity and cyberwafare.
But some analysts said the latest incident did not appear particularly professional.
"This looks like a fairly crass attempt at intelligence-gathering," said John Bassett, a former senior official at Britain's signals intelligence agency GCHQ and now associate fellow at the Royal United Services Institute.
"It's incompetent in that the intruders were spotted quickly. The targeting looks wholesale and rather random... It feels like an effort by B-team players that's gone badly wrong."