Is NSA surveillance really necessary to defend against terrorist attacks? Its been a common claim by the agencys defenders as the programs come under scrutiny, but a report released today by the New America Foundation casts doubt on that logic. The report examines how NSA surveillance functioned in 225 counterterrorism cases since 9/11 and concludes that the agency wasnt as crucial as it would have you believe. The report found that the NSA was responsible for 7.5% of counterterrorism investigations, and there was only one case out of the 225 that was initiated by NSA evidence.