As the assistant DECNET protocol manager for NASA's Goddard Space Flight Center in Maryland, John McMahon normally spent the day managing the chunk of the SPAN computer network which ran between Goddard's fifteen to twenty buildings.

McMahon worked for Code 630.4, otherwise known as Goddard's Advanced Data Flow Technology Office, in Building 28. Goddard scientists would call him up for help with their computers. Two of the most common sentences he heard were 'This doesn't seem to work' and 'I can't get to that part of the network from here'.

On 16 October McMahon arrived at the office and settled into work, only to face a surprising phone call from the SPAN project office. Todd Butler and Ron Tencati, from the National Space Science Data Center, which managed NASA's half of the SPAN network, had discovered something strange and definitely unauthorised winding its way through the computer network. It looked like a computer worm.

A computer worm is a little like a computer virus. It invades computer systems, interfering with their normal functions. It travels along any available compatible computer network and stops to knock at the door of systems attached to that network. If there is a hole in the security of the computer system, it will crawl through and enter the system. When it does this, it might have instructions to do any number of things, from sending computer users a message to trying to take over the system. What makes a worm different from other computer programs, such as viruses, is that it is self-propagating. It propels itself forward, wiggles into a new system and propagates itself at the new site. Unlike a virus, a worm doesn't latch onto a data file or a program. It is autonomous.

At the SPAN centre, things were becoming hectic. The worm was spreading through more and more systems and the phones were beginning to ring every few minutes. NASA computers were getting hit all over the place.

The SPAN project staff needed more arms. They were simultaneously trying to calm callers and concentrate on developing an analysis of the alien program. Was the thing a practical joke or a time bomb just waiting to go off? Who was behind this?

NASA was working in an information void when it came to WANK. Some staff knew of the protesters' action down at the Space Center, but nothing could have prepared them for this. NASA officials were confident enough about a link between the protests against Galileo and the attack on NASA's computers to speculate publicly that the two were related. It seemed a reasonable likelihood, but there were still plenty of unanswered questions.

Callers coming into the SPAN office were worried. People at the other end of the phone were scared. Many of the calls came from network managers who took care of a piece of SPAN at a specific NASA site, such as the Marshall Space Flight Center. Some were panicking; others spoke in a sort of monotone, flattened by a morning of calls from 25 different hysterical system administrators. A manager could lose his job over something like this.

Most of the callers to the SPAN head office were starved for information. How did this rogue worm get into their computers? Was it malicious? Would it destroy all the scientific data it came into contact with? What could be done to kill it?

NASA stored a great deal of valuable information on its SPAN computers. None of it was supposed to be classified, but the data on those computers is extremely valuable. Millions of man-hours go into gathering and analysing it. So the crisis team which had formed in the NASA SPAN project office, was alarmed when reports of massive data destruction starting coming in. People were phoning to say that the worm was erasing files.

It was every computer manager's worst nightmare, and it looked as though the crisis team's darkest fears were about to be confirmed.

Yet the worm was behaving inconsistently. On some computers it would only send anonymous messages, some of them funny, some bizarre and a few quite rude or obscene. No sooner would a user login than a message would flash across his or her screen:


Remember, even if you win the rat race-you're still a rat.

Or perhaps they were graced with some bad humour:
Nothing is faster than the speed of light...
To prove this to yourself, try opening the refrigerator
door before the light comes on.

Other users were treated to anti-authoritarian observations of the paranoid:

The FBI is watching YOU.
or

Vote anarchist.

But the worm did not appear to be erasing files on these systems. Perhaps the seemingly random file-erasing trick was a portent of things to come - just a small taste of what might happen at a particular time, such as midnight. Perhaps an unusual keystroke by an unwitting computer user on those systems which seemed only mildly affected could trigger something in the worm. One keystroke might begin an irreversible chain of commands to erase everything on that system.

The NASA SPAN computer team were in a race with the worm. Each minute they spent trying to figure out what it did, the worm was pushing forward, ever deeper into NASA's computer network. Every hour NASA spent developing a cure, the worm spent searching, probing, breaking and entering. A day's delay in getting the cure out to all the systems could mean dozens of new worm invasions doing God knows what in vulnerable computers. The SPAN team had to dissect this thing completely, and they had to do it fast.

Some computer network managers were badly shaken. The SPAN office received a call from NASA's Jet Propulsion Laboratories in California, an important NASA centre with 6500 employees and close ties to California Institute of Technology (Caltech).

JPL was pulling itself off the network.

This worm was too much of a risk. The only safe option was to isolate their computers. There would be no SPAN DEC-based communications with the rest of NASA until the crisis was under control. This made things harder for the SPAN team; getting a worm exterminating program out to JPL, like other sites which had cut their connection to SPAN, was going to be that much tougher. Everything had to be done over the phone.

Worse, JPL was one of five routing centres for NASA's SPAN computer network. It was like the centre of a wheel, with a dozen spokes branching off - each leading to another SPAN site. All these places, known as tailsites, depended on the lab site for their connections into SPAN. When JPL pulled itself off the network, the tailsites went down too.

It was a serious problem for the people in the SPAN office back in Virginia. To Ron Tencati, head of security for NASA SPAN, taking a routing centre off-line was a major issue. But his hands were tied. The SPAN office exercised central authority over the wide area network, but it couldn't dictate how individual field centres dealt with the worm. That was each centre's own decision. The SPAN team could only give them advice and rush to develop a way to poison the worm.


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