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APPROACHING ZERO

had alerted SCICON to Bach and Handel. A hacker coming in the back door would be conspicuous because the ID and password used - the ones entered in the log - could be any combination of random characters; they wouldn't necessarily be real IDs and passwords, and their inclusion in the log would alert even a sleepy system operator to the existence of intruders.

The solution was to capture the identity of legitimate users, especially ones with high privileges. Then hackers could roam through the system secretly, masquerading as authorized users.

To this end Weihruch had developed a specialist tool to capture IDs and passwords as they were entered. This tool - in reality, a program - replaced the real entry screen with a phoney, a complete replica that was indistinguishable to a user. On seeing the screen, the unsuspecting user would enter his ID in the normal way, followed by his password. The program captured that information, saving it on a secret file. Then, because it wasn't able to allow entry, the phoney screen displayed the message 'invalid - please reenter'. The user would think he had simply miskeyed his password. For his next attempt, the user would be presented with the proper screen; if all was in order, he would be able to gain access.

The hacker could then pick up the secret file, containing all the IDs and passwords that it had collected, on his next visit. It was like using traps to catch rabbits, except that the rabbit didn't feel a thing. The program had automated hacking. With legitimate IDs and the back-door entry system, hacking became simply a matter of finding VAX computers, going in through the back door, leaving the trap program to function until it had captured some legitimate identities, then taking the real IDs and passwords from the file.

With the back door and the trap program, Pengo and Koch were able to supply the Soviets with better material. Koch passed Kahl computer log-ins, passwords to military systems. In return, Kahl passed back money.

But despite the success with VMS, the KGB was upping the ante again. The Soviets passed word that they wanted Koch and Pengo to hack into computers that used the UNIX operating system. UNIX was becoming increasingly popular because it could be used on a wide range of computers; many VAX users preferred UNIX to VMS,

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