The Snowden leaks have taught us much about the tactics employed by the NSA and GCHQ, from brazen malware attacks to more esoteric dark arts, such as infecting low-level pieces of computer code. Correspondingly, research into more surreptitious activities targeting the guts of modern systems has often been overshadowed by studies of more obvious attacks. Yet such high-tech techniques pose a more severe risk. They can, for instance, allow agencies to spy on Tails, the Linux-based secure operating system favored by Snowden. And they’re not as difficult to exercise as many would imagine. They can totally obliterate the privacy of even the most careful computer user.