Government-created viruses for surveillance

From John Twelve Hawks’s “ How We Live Now” (2005):

The Traveler describes for the first time in any book the secret computational immunology programs being developed in Britain. These programs behave like the leucocytes floating through our bloodstream. The programs wander through the Internet, searching, evaluating, and hiding in a person’s home PC, until they detect a “dangerous” statement or unusual information. After gathering our personal information, they return to the central computer. There is no reason why they can’t easily be programmed to destroy a target computer … such as the one on which you’re reading this essay.