The Washington Post has revealed that it is among the latest US companies targeted by cyber attacks following similar security breaches with the Wall Street Journal, New York Times and Twitter.
The US newspaper confirmed the attack in 2011 in an article published on its website on Friday, which said it suspected Chinese hackers.
“Like other companies in the news recently, we face cyber security threats,” Post spokeswoman Kris Coratti said in an article published on the Post's website.
“In this case, we worked with [security company] Mandiant to detect, investigate, and remediate the situation promptly at the end of 2011. We have a number of security measures in place to guard against cyber attacks on an ongoing basis.”
The cyber attack comes days after Twitter, the popular micro-blog site and US newspapers the New York Times and the Wall Street Journal revealed their respective websites had been the target of a co-ordinated hacking effort.
The newspapers blamed China for the attack, while Twitter, which is still trying to recover for a breach that affected about 250,000 accounts, did not suggest the same.
China has been accused of a widespread and aggressive cyber-spying campaign for several years, but the country's foreign ministry has denied the claims.