Is there any particular reason why you don't believe the fact sheet from the Director of National Intelligence[1] or Marc Ambinder[2]?
According to these sources (selected excerpts):
> PRISM is not an undisclosed collection or data mining program.
> PRISM is a kick-ass GUI that allows an analyst to look at, collate, monitor, and cross-check different data types provided to the NSA from internet companies located inside the United States.
> All such information is obtained with FISA Court approval and with the knowledge of the provider based upon a written directive from the Attorney General and the Director of National Intelligence.
1. https://docs.google.com/file/d/0B8dPmI7DfkxMejNyazZYMl93dlk/...
2. http://theweek.com/article/index/245360/solving-the-mystery-...