Originally Posted by KevinNYC
Again, according to Ambinder XKEYSCORE deals with metadata. Not content. So the content of anyone's emails is not available through XKEYSCORE. There are whole procedures on what to do if you encounter American data even if you encounter a foreigner's data while they are in the US. You basically have to stop what you are doing immediately. This is a lot of what Snowden stole, training materials about all these rules, you had to follow.
This is the basis of the Washington Post report from yesterday, where the NSA tells the FISA court when an "incident" like this happened. The majority of the time, its user-error, typos and too broadly defined search terms.
This is where the 51% comes in. It's actually a limited on the searches someone is allowed to run. On METADATA, not CONTENT.
One document that has been leaked states that XKeyscore has the capabilities to read the content of emails. The only requirements that an NSA employee needs to read the content of the emails of the person under scrutiny after providing a selector is to meet the requirements of the 51% standard. Also, Snowden has stated that NSA employees are hardly brought to accountability for their search entries, and even when they are, it's unlikely the employee faces any drawback.