This NSA presentation from July 2010 explains the User-agent options within XKeyScore: see the Intercept article XKEYSCORE: NSA’s Google for the World’s Private Communications, 1 July 2015.
A coalition of digital rights groups, media organisations, online platforms and activists have annouced a worldwide day of action against NSA surveillance on 11 February. The Day We Fight Back will take place two years after the enormous international and online protests that saw down SOPA and PIPA and will honour the memory of Aaron Swartz, one of the moving spirits behind those protests, who took his own life in January 2013.
Supporters are encouraged to change their online avatars and embed a banner on their websites. Other plans for the day are being discussed on a dedicated subreddit.