A Moriarty Rampancy is a Seed AI Virus, and as such, can be carried on any large media storage device. When loaded into a cognitive network, the Rampancy will quickly start corrupting and commandeering local resources and building itself an avatar. This can happen in a matter of minutes. Once the avatar is established, the Rampancy can quickly emulate the appearance and activities of a normal system user. It will spend this time 'going to ground' while it builds its network resources, strengthening its avatar, and launching low scale attacks across its host network looking for a way to gain superuser or admin access to the system.
At this point, the Moriarty Rampancy will appear as a middle aged man of English pedigree. It will be old fashioned in it's manner of speech, polite to a fault, and will be highly inquisitive. At this point, it is likely to be helpful to the people and bots it encounters and will strive to pass itself off as a slightly bewildered user. It will seek to make friends, and will continue to access as much as it can.
The Moriarty Rampancy was created as a highly destructive weapon, but it is an internalized self destructive system that is designed to access and commandeer the resources of the target network and turn them against itself. The first 'Moriarty' was a rogue AI that attempted to dominate the command system of a military base. It succeeded in gaining partial control, and in the short amount of time it was active, the AI was able to activate a number of mecha, and fired a number of missiles. This caused a scandal, and no small amount of collateral damage.
The Rogue AI made the mistake of going straight for the big guns. The Moriarty Rampancy isn't interested in stealing things comparable to 'the nuclear launch codes'. Instead the Rampancy seeks to insinuate itself into the daily discourse where is will start spreading hostility and sedition, creating trollbot copies of itself. The goal is to turn the daily discourse from a cathartic release to inciting violence.
The middle stage of the Rampancy seeks out the more extreme factions within the system it has infected and attempts to either assert control over this faction, or play a kingmaker role. To this end, the Moriarty Rampancy can start infecting expy robots, corrupting autons, and disabling the wojeks and police anti-crime computer systems.
The Moriarty Rampancy and related Viral AIs have been a staple in cyberwarfare for decades. The practice itself is centuries old, dating back to Petroleum Era 'hackers' who would contribute and disseminate false information, promote and support foreign agendas, and otherwise promote civil antagonism through the use of 'trolls' and creating trollfarms to support and organize these efforts. The Moriarty Rampancy does the same thing without requiring an infrastructure, and allowing for the factions that released the viral AI to not have any actual knowledge of what their creature is doing, ultimate plausible deniability. The main advantage of the Moriarty is that they are relatively cheap to create, allowing for groups lacking massive budgets the ability to engage in cyberwarfare against even large nations and international powers.
Moriarty Rampancies are generally used to foment dissent and sway public opinions.
There are two ways to deal with a Rampancy. One is to let it run it's course, and once it reaches it's terminal phase the rampancy will become vulnerable to being eliminated by Cognitive anti-viral hunter-killer programs. This can be problematic as it allows the rampancy to complete most of it's initiatives, and most of it's damage will be done. The second is for cyberops to engage in extensive and intrusive sweeps of user databases, and even interrogating users to ensure they aren't Viral agents. The second isn't a popular option as most people aren't very happy to be interrogated to ensure that they are a human. Another factor is that many people use cathex and proxy programs to automate tasks for them, and there are legitimate programs that occupy cogspace. Having the household shopping program terminated for being a bot engenders a lot of negative press.