NSA program reportedly allows analysts to track emails, chats, web searches

The National Security Agency is operating a massive database system that allows analysts to scour individuals' emails, chats and Internet browsing histories at will, according to a new report from The Guardian based on leaked documents.
The article was quickly challenged by the NSA. In a statement forwarded to Fox News, the agency said "allegations of widespread, unchecked analyst access to NSA collection data are simply not true."
The agency acknowledged the existence of the program -- called XKeyscore -- but said access is limited and suggested it...