In the darkest places of the internet, there lie dark relics of the past. Before the Crash, these relics were mere hinderences. Now that the Internet is a much more dangerous place, these artifacts are chemical weapons of mass destruction.
They often come in the form of large metallic briefcases. Contained within are several metallic, opaque vials containing millions of microscopic viruses. They lie dormant in the air and even when they come into contact with potential victims, they still remain sluggish, carrying no negative effect. They simply breed inside their victims, leaping from those victims to other victims. Very quickly, countless humans can become hosts to this strange virus.
There is another section to the briefcase. A keyboard, a screen, a key and a keyhole. Often, the screen contains the name of a long lost webfort. A new name can be entered, of a new webfort. The key can be inserted into the hole and the key can be turned.
Suddenly, throughout the internet, the virus gains control of the host's interface and begins to mass produce at a massive rate, leaving a trail of mist behind it as it sprints towards its location like a rabid dog. In less than a second, the webfort finds itself overwhelmed by countless victims of the virus, all of them spewing out that horrible mist. The mist becomes a fog. The fog becomes a barrier. All it takes is another second and all that is left of the webfort is a massive green cloud. Nothing comes in, nothing comes out. Not even communications. The virus-cloud breeds and breeds, expanding and expanding until it has no further energy to spend - it cannot breed any further. Eventually, each virus dies and the cloud swindles. The process takes days but eventually the mist parts and all that is left is a ghost town.
The briefcase has one more trait. On it, are four letters.