From his income as a member of the state students' council, he bought his first computer in 1982 and named it "FUCKUP" ("First Universal Cybernetic-Kinetic Ultra-Micro Programmer") after The Illuminatus!

In February 1987 Koch broke off a vacation in Spain, because of this, and had himself admitted to a psychiatric clinic in Aachen for rehab treatments, where he stayed for three months.

He worked with the hackers known as DOB (Dirk-Otto Brezinski), Pengo (Hans Heinrich Hübner), and Urmel (Markus Hess), and was involved in selling hacked information from United States military computers to the KGB.

Clifford Stoll's book The Cuckoo's Egg gives a first-person account of the hunt and eventual identification and arrest of Hess in March 1989.

The remains of Koch—at this point just bones[2]—were discovered close by with a patch of scorched and burnt ground surrounding them and with his shoes missing.