The Washington Post disclosed on Saturday that it had suffered a cyberattack and suspects Chinese hackers were behind it, joining Twitter and major US media outlets that have endured intrusions.
The Post said in a front page story that the attack was detected in 2011. It said Post company officials would not comment on the circumstances, duration of the intrusion or apparent origin.
The paper quoted Post spokeswoman Kris Coratti as saying the paper worked with a security company to detect, investigate and resolve the situation "promptly" at the end of 2011.
"We have a number of security measures in place to guard against cyberattacks on an ongoing basis," Coratti was quoted as saying.
The revelation came after Twitter said on Friday it was hammered by a sophisticated cyber attack similar to those that recently hit the news outlets.
Twitter said the passwords of about 250,000 users were stolen.
This week the New York Times and the Wall Street Journal both accused Chinese hackers of targeting their computers in an apparent effort to spy on journalists covering China.