US: America's biggest intelligence agency has admitted placing tracking cookies that can monitor internet activity on the computers of visitors to its website, despite federal rules banning the practice.
The National Security Agency (NSA) removed the cookies from its site after Daniel Brandt, a computer privacy activist, complained.
The agency said the cookies were placed on the site by mistake during a software update.
Federal agencies are banned from using "persistent cookies" - which are not deleted automatically after users close their web browsers - unless "there is a compelling need to gather the data".
Cookies are small files generated by web servers and stored in the computers of website users, ready for access by the server the next time the user visits the website.
They are widely used by commercial websites to make internet browsing and shopping easier by remembering passwords and preferences.
Privacy advocates such as Mr Brandt acknowledge that cookies can be useful but are concerned about the spread of persistent cookies which can stay in a user's computer for up to 30 years, often tracking web activity.
Most computer users are unaware of the cookies stored on their hard drive, many of which contain information that is shared by a number of commercial organisations.
The federal government introduced restrictions on the use of cookies after it was discovered that the White House drug policy office tracked computer users who viewed its anti-drug information pages.
The NSA, which employs 30,000 people, is America's most shadowy intelligence agency as well as its biggest.
President George W Bush admitted earlier this month that he had secretly authorised the NSA to spy on international phone calls made to and from US citizens, a practice some congressmen believe is illegal.
Mr Bush claims he was entitled to order the eavesdropping as a commander-in-chief directing the war on terror.
The administration this week accused an appeals court of trying to "usurp" the president's authority as commander-in-chief by refusing to allow the immediate transfer of a terrorist suspect from military to civilian custody.
After 3½ years held in a military prison, Jose Padilla, who is a US citizen, was charged last month in a civilian court in Miami. The civilian charges came a day after Mr Padilla's lawyers had told the supreme court that Mr Bush had overstepped his authority in jailing him as an enemy combatant.
But an appeals court in Virginia said that the administration appeared to be manipulating the system by trying to change Mr Padilla's status to avoid a supreme court decision that could have found he was being held unlawfully.
Administration lawyers this week asked the supreme court to allow Mr Padilla to be transferred to a civilian prison, accusing the appeals court of defying "both law and logic".
The brief said that the court did not have the authority to disregard a directive from the president and described the ruling as "an unwarranted attack on the exercise of executive discretion".