However, Joe was just an average user. He didn't have root, which is what Mendax wanted. But like every other user on the system, Joe had a user identity number. Mendax changed Joe's user id to `0'--the magic number. A user with `0' as his id had root. Joe had just acquired power usually only given to system administrators. Of course, Mendax could have searched out a user on the list who already had root, but there were system operators logged onto the system and it might have raised suspicions if another operator with root access had logged in over the dial-up lines. The best line of defence was to avoid making anyone on the system suspicious in the first place. The problem now was to replace the original ETC directory with the Trojan one. Mendax did not have the privileges to delete the legitimate ETC directory, but he could change the name of a directory. So he changed the name of the ETC directory to something the computer system would not recognise. Without access to its list of users, the computer could not perform most of its functions. People would not be able to log in, see who else was on the system or send electronic mail. Mendax had to work very quickly. Within a matter of minutes, someone would notice the system had serious problems. Mendax renamed his Trojan directory ETC. The system instantly read the fake directory, including Joe's now non-existent password, and elevated status as a super-user. Mendax logged in again, this time as Joe. In less than five minutes, a twenty-year-old boy with little formal education, a pokey $700 computer and painfully slow modem had conquered the Melbourne computer system of one of the world's largest telecommunications companies. There were still a few footprints to be cleaned up. The next time Joe logged in, he would wonder why the computer didn't ask for his password. And he might be surprised to discover he had been transformed into a super-user. So Mendax used his super-user status to delete the Trojan ETC file and return the original one to its proper place. He also erased records showing he had ever logged in as Joe. To make sure he could login with super-user privileges in future, Mendax installed a special program which would automatically grant him root access. He hid the program in the bowels of the system and, just to be safe, created a special feature so that it could only be activated with a secret keystroke. Mendax wrestled a root account from NMELH1 first, but Prime Suspect wasn't far behind. Trax joined them a little later. When they began looking around, they could not believe what they had found. The system had one of the weirdest structures they had ever come across. Most large networks have a hierarchical structure. Further, most hold the addresses of a handful of other systems in the network, usually the systems which are closest in the flow of the external network.