The virus that ate through Da5id's brain was a string of binary information, shone into his face in the form of a bitmap -- a series of white and black pixels, where white represents zero and black represents one. They put the bitmap onto scrolls and gave the scrolls to avatars who went around the Metaverse looking for victims.
The Clint who tried to infect Hiro in The Black Sun got away, but he left his scroll behind -- he didn't reckon on having his arms lopped off -- and Hiro dumped it into the tunnel system below the floor, the place where the Graveyard Daemons live. Later, Hiro had a Daemon take the scroll back to his workshop. And anything that is in Hiro's house is, by definition, stored inside his own computer. He doesn't have to jack into the global network in order to access it.
It's not easy working with a piece of data that can kill you. But that's okay. In Reality, people work with dangerous substances all the time -- radioactive isotopes and toxic chemicals. You just have to have the right tools: remote manipulator arms, gloves, goggles, leaded glass. And in Flatland, when you need a tool, you just sit down and write it. So Hiro starts by writing a few simple programs that enable him to manipulate the contents of the scroll without ever seeing it.
The scroll, like any other visible thing in the Metaverse, is a piece of software. It contains some code that describes what it looks like, so that your computer will know how to draw it, and some routines that govern the way it rolls and unrolls. And it contains, somewhere inside of itself, a resource, a hunk of data, the digital version of the Snow Crash virus.
Once the virus has been extracted and isolated, it is easy enough for Hiro to write a new program called SnowScan. SnowScan is a piece of medicine. That is, it is code that protects Hiro's system -- both his hardware and, as Lagos would put it, his bioware -- from the digital Snow Crash virus. Once Hiro has installed it in his system, it will constantly scan the information coming in from outside, looking for data that matches the contents of the scroll. If it notices such information, it will block it.
There's other work to do in Flatland. Hiro's good with avatars, so he writes himself an invisible avatar -- just because, in the new and more dangerous Metaverse, it might come in handy. This is easy to do poorly and surprisingly tricky to do well. Almost anyone can write an avatar that doesn't look like anything, but it will lead to a lot of problems when it is used. Some Metaverse real estate -- including The Black Sun -- wants to know how big your avatar is so that it can figure out whether you are colliding with another avatar or some obstacle. If you give it an answer of zero -- you make your avatar infinitely small -- you will either crash that piece of real estate or else make it think that something is very wrong. You will be invisible, but everywhere you go in the Metaverse you will leave a swath of destruction and confusion a mile wide. In other places, invisible avatars are illegal. If your avatar is transparent and reflects no light whatsoever -- the easiest kind to write -- it will be recognized instantly as an illegal avatar and alarms will go off. It has to be written in such a way that other people can't see it, but the real estate software doesn't realize that it's invisible.
There are about a hundred little tricks like this that Hiro wouldn't know about if he hadn't been programming avatars for people like Vitaly Chernobyl for the last couple of years. To write a really good invisible avatar from scratch would take a long time, but he puts one together in several hours by recycling bits and pieces of old projects left behind in his computer. Which is how hackers usually do it.
While he's doing that, he comes across a rather old folder with some transportation software in it. This is left over from the very old days of the Metaverse, before the Monorail existed, when the only way to get around was to walk or to write a piece of ware that simulated a vehicle.
In the early days, when the Metaverse was a featureless black ball, this was a trivial job. Later on, when the Street went up and people started building real estate, it became more complicated. On the Street, you can pass through other people's avatars. But you can't pass through walls. You can't enter private property. And you can t pass through other vehicles, or through permanent Street fixtures such as the Ports and the stanchions that support the monorail line. If you try to collide with any of these things, you don't die or get kicked out of the Metaverse; you just come to a complete stop, like a cartoon character running spang into a concrete wall.
In other words, once the Metaverse began to fill up with obstacles that you could run into, the job of traveling across it at high speed suddenly became more interesting. Maneuverability became an issue; Size became an issue. Hiro and Da5id and the rest of them began to switch away from the enormous, bizarre vehicles they had favored at first -- Victorian houses on tank treads, rolling ocean liners, mile-wide crystalline spheres, flaming chariots drawn by dragons -- in favor of small maneuverable vehicles. Motorcycles, basically.
A Metaverse vehicle can be as fast and nimble as a quark. There's no physics to worry about, no constraints on acceleration, no air resistance. Tires never squeal and brakes never lock up. The one thing that can't be helped is the reaction time of the user. So when they were racing their latest motorcycle software, holding wild rallies through Downtown at Mach 1, they didn't worry about engine capacity. They worried about the user interface, the controls that enabled the rider to transfer his reactions into the machine, to steer, accelerate, or brake as quickly as he could think. Because when you're in a pack of bike racers going through a crowded area at that speed, and you run into something and suddenly slow down to a speed of exactly zero, you can forget about catching up. One mistake and you've lost.
Hiro had a pretty good motorcycle. He probably could have had the best one on the Street, simply because his reflexes are unearthly. But he was more preoccupied with sword fighting than motorcycle riding.
He opens up the most recent version of his motorcycle software, gets familiar with the controls again. He ascends from Flatland into the three-dimensional Metaverse and practices riding his bike around his yard for a while. Beyond the boundaries of his yard is nothing but blackness, because he's not jacked into the net. It is a lost, desolate sensation, kind of like floating on a life raft in the Pacific Ocean.
Sometimes they see boats in the distance. A couple of these even swing close by to check them out, but none of them seems to be in that rescuing mood. There are few altruists in the vicinity of the Raft, and it must be evident that they don't have much to steal.
From time to time, they see an old deep-water fishing boat, fifty to a hundred feet long, with half a dozen or so small fast boats clustered around it.
When Eliot informs them that these are pirate vessels, Vic and Fisheye prick up their ears. Vic unwraps his rifle from the collection of Hefty bags that he uses to protect it from the salt spray, and detaches the bulky sight so that they can use it as a spyglass. Hiro can't see any reason to pull the sight off the rifle in order to do this, other than the fact that if you don't, it looks like you're drawing a bead on whatever you're looking at.
Whenever a pirate vessel comes into view, they all take turns looking at it through the sight, playing with all the different sensor modes: visible, infrared, and so on. Eliot has spent enough time knocking around the Rim that he has become familiar with the colors of the different pirate groups, so by examining them through the sight he can tell who they are: Clint Eastwood and his band parallel them for a few minutes one day, checking them out, and the Magnificent Seven send out one of their small boats to zoom by them and look for potential booty. Hiro's almost hoping they get taken prisoner by the Seven, because they have the nicest-looking pirate ship: a former luxury yacht with Exocet launch tubes kludged to the foredeck. But this reconnaissance leads nowhere. The pirates, unschooled in thermodynamics, do not grasp the implications of the eternal plume of steam coming from beneath the life raft.
One morning, a big old trawler materializes very close to them, congealing out of nothing as the fog lifts. Hiro has been hearing its engines for a while, but didn't realize how close it was.