New documents leaked by former National Security Agency contractor Edward Snowden say that the agency is using small tracking files, known as "cookies," to help select targets for hacking and broader surveillance.

The Washington Post reports that the NSA and its British counterpart, GCHQ, are using the cookies to identify people browsing the Internet. The files contain numeric codes that enable websites to identify a specific person's browser.

According to slides leaked by Snowden to The Post, a particular cookie can also allow the NSA to single out an individual's online communications and send out software that can hack the person's computer. In particular, the report claims that the NSA has gotten much use out of the Google-specific "PREF" cookie, which is assigned to a browser anytime a connection is made to one of the Google's Web properties or services.

According to the Post, cookie information is one of the data forms that the NSA can gain access to with a Foreign Intelligence Surveillance Act order from a special court. When an order is granted by the court, the company is notified and is compelled to assist the NSA.

Privacy advocates have long argued that consumers should be allowed to opt out of being tracked commercially. Technology companies like Google use cookies as part of an ad-driven business model that pays for customer services like e-mail.

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The report comes after Google joined seven other leading technology companies Monday in calling for increased restrictions on government surveillance, including an end to bulk collecting of user data and a limit on court-approved surveillance requests.

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