Blackwall

The Blackwall is a virtual wall that is said to keep free A.I.s from breaking through into the rest of the virtual world and wreaking havoc, possibly causing the end of the world along with it. To ensure this never happens, NetWatch works to keep others from destroying it. However, other groups, like the Voodoo Boys, believe the free A.I.s will help them conquer the virtual world and thus look for ways to destroy the Blackwall.

It's believed that NetWatch was only able to construct the Blackwall because the Free A.I.'s wanted to be left alone and in control of vast abandoned sections of the old net. The Blackwall often splits old network systems in half leading to stories of haunted data.