12/12/13: The BBC reports the latest leak suggests US and UK cyberspies are taking advantage of Google's proprietary cookie technology in an effort to track suspects. Documents published by the Washington Post refer to the NSA and GCHQ's use of "GooglePrefIDs" - files containing a numeric code placed on computers to help the search firm remember users. The paper said the US and UK spy agencies piggybacked the files to "home in" on targets already under suspicion. Google has not commented. However, the news may add to existing tensions between the firm and the authorities. Google's chairman Eric Schmidt said last week that the company had considered moving its servers outside of the US following the publication of earlier leaks, before deciding it was impractical.