British and American spy agencies use mobile phone applications such as the game Angry Birds to gain access to users' personal data, leaked documents revealed.
GCHQ, the government's listening post, and the US National Security Agency (NSA) are using smartphone applications to gather private details such as age, gender and location, as well as contacts and websites visited.
Some applications can even share sensitive information, such as sexual orientation, marital status and income, it was claimed.
The disclosure comes in the latest round of classified documents provided by the whistleblower Edward Snowden, published in the Guardian, the New York Times and ProPublica.
The reports suggest data is gleaned through mapping, gaming and social networking apps, using techniques similar to those used to intercept text message data and mobile internet traffic.
Most major social media websites, such as Facebook and Twitter, remove metadata that can give away information about location from photographs before they are published, the Guardian said.
But during the uploading process data can, briefly, be available for collection by spying agencies.
Depending on a user's profile information, the documents suggested, agencies could then collect almost every useful detail about a person, including home country, current location, age, gender, postcode, marital status, income, ethnicity, education, sexual orientation and number of children.
One NSA document from 2010, entitled Golden Nugget, described a "perfect scenario" in which the agency could gather a broad range of information from a photo uploaded to a social media site from a mobile phone, including phone lists, websites visited and documents downloaded.
Intercepting Google Maps queries was so successful in collecting data that "anyone using Google Maps on a smartphone is working in support of a GCHQ system", another document revealed.
And other papers set out examples of what information on users can be extracted through games such as Angry Birds, which has been downloaded more than 1.7 billion times across the world.
Rovio, the maker of Angry Birds, told the Guardian it had no involvement with GCHQ or the NSA, and that it didn't have any previous knowledge of the matter.
GCHQ told the newspaper its activities were proportional and complied with UK law.
A spokesman said: "It is a longstanding policy that we do not comment of intelligence matters. All of GCHQ's work is carried out in accordance with a strict legal and policy framework which ensures that our activities are authorised, necessary and proportionate, and that there is rigorous oversight."