According to documents leaked to Der Spiegel, the NSA sells a $40,000 "active GSM base station" to be used as a tool to mimic a mobile phone tower and thus monitor cell phones.
根据迪耶·斯皮格尔（Die Spiegel）所泄露出的文档，NSA销售了4万美元的“活跃GSM基站”，被用作一个工具来伪装一个移动电话塔，并然后监视蜂窝电话。