A new set of classified documents disclosed on Sunday suggested that Edward Snowden, the former National Security Agency contractor who has provided a trove of documents to the Guardian newspaper, had obtained a wider range of materials about government surveillance than had been known, including one document detailing how American and British intelligence agencies had eavesdropped on world leaders at a conference in London in 2009.
The Guardian reported Sunday night that Government Communications Headquarters, or GCHQ, the British eavesdropping agency that works closely with the NSA, monitored the email and phones of other countries' representatives at two meetings at the London conference. In addition, it said, the United States intercepted the communications of Dmitry Medvedev, then the Russian president and now the prime minister.
The Guardian posted some GCHQ documents on its website with part of the contents blacked out. A spokesman for the Guardian said on Sunday that the paper decided on its own to redact the documents, and that enough was published to show the authenticity of the report.
Richard Aldrich, professor of international security at the University of Warwick and the author of a history of GCHQ, said the logos of the NSA and Canadian intelligence on one of the British documents suggested that they were accessible to Snowden "under the auspices of a joint program."
He said Snowden's leak shows that British and American diplomats and politicians get a real-time feed of intelligence on their counterparts at major summits.
U.S. intelligence officials have expressed alarm at the variety of highly classified material Snowden obtained, suggesting that his actions reveal a shocking breach in the fundamental principle that intelligence officers should have access only to the data they need to do their jobs.