The Daily Northwestern, Tuesday, November 12, 1985 (Vol 107, No. 37)

NU frosh programs cloning achievement

Computer virus catchy, not fatal

By Mike Sprengelmeyer, Daily Reporter

"Hey Skrenta," they used to say in the high school computer lab. "Have any new games this week?"

But that was back in Pittsburgh and before CAS freshman Richard Skrenta became mildly famous for his programming mischief. Now his "games" are not taken so lightly.

Time Magazine found out about Skrenta's work and included him in a story in its Nov. 4 issue. Back in March, he made his magazine debut in Scientific American.

All this fame for a program he wrote in the ninth grade.

"Some of my friends thought it was funny," said Skrenta. "Most of them hated it."

"Cloner" was Skrenta's baby. When a disk containing Cloner was inserted into the computer, a "virus" would wait inside the computer for another disk to be inserted. Then the contagious virus would attach itself to the new disk and have its fun.

Skrenta's virus counts the times the infected disk is inserted in the computer. Every few times, Cloner would make subtle changes in the workings of the program so that minor flaws would appear in the output.

Every 50th use, the virus would cause the screen to go blank, allowing Skrenta's poem to appear:

     Elk Cloner:  The program with a personality

        It will get on all your disks
          It will infiltrate your chips
            Yes it's Cloner!
 
        It will stick to you like glue
          It will modify ram too
            Send in the Cloner!

None of the mischief that Cloner did was permanent. A quick flick of the on/off switch and a re-insertion of the disk would restore the program. The problem with Cloner lay in its name. Cloner would stay in the computer if it was not turned off, continuing to copy itself onto other disks.

There is no immunization yet against computer viruses. So before long, Skrenta, his friends and even one of his math teachers, discovered their disk libraries suffered from Skrenta's plague.

Skrenta didn't know just how his math teacher got a copy of Cloner on his disks. "He said if I would have been there (when he read the poem), he would have broken my neck," Skrenta said. "We were (friends) before that, but he didn't appreciate me much after."

The story in Scientific American included two Italian programmers who came up with a similar virus idea. Roberto Cerruti, writing for the two in the magazine, said: "The awful evil of our idea was clear, and we decided neither to carry it out, nor to speak to anybody about the idea."

Skrenta said he know such a program might do no good. He decided to write it anyway.

Bob Hablutzel, a programming analyst at Vogelback Computing Center, said the program was "probably a pretty neat piece of code."

While simple viruses can be fairly easy to write, complex ones like Skrenta's can be "extremely hard to do," Hablutzel said.

He said Skrenta has a considerable degree of programming talent, albeit "misdirected."


Rich Skrenta (skrenta@pbm.com)