A CVI, also known as a Cyber-virus, was a device of Taelon origin which were described as being part Taelon germ and part computer chip. (Episode: Decision)
They were implants that were typically placed within the body of Companion Protectors and programmed with a number of directives that aimed at improving the operative. They increased basic intelligence and memory recall; allowing users to experience their memory again. However, they also altered the hosts motivational imperative to favor the Companions. (Episode: Decision) The cyber viral implant was capable of giving its host the capacity to relive memories in complete details; sights, sounds and smells. Every impression was remembered no matter how remote it was - these events were known as memory intrusions. Initially, hosts struggled to control them but in time, the cerebral cortex adapted and used it as another way of thinking. The increased intelligence allowed hosts to multitask allowing them to go through multiple computer screens at high speed whilst absorbing the contents presented to them. (Episode: Truth) A lesser known protocol within the CVI's was that they were designed to ensure absolute loyalty to the Taelons and prevented the host from acting in a way harmful to them. (Episode: Atavus) CVI's were eventually discovered to have a lifespan of two years whereupon the implant died and potentially killed the host with it.
Doctor Jullianne Belman managed to create an Anti-Cybervirus which was designed to break down the CVI implant before it degeneration killed its host. The process was designed to work over a twenty hour period in order to ensure the host survived as it was difficult to fix the neurological changes the CVI had placed on the brain. It was known that when the implants were first created, the first generation of hosts were given by the Taelon's enhanced knowledge about their goals on Earth in order to better their abilities. However, it was decided that future generations of CVI implants did not need to know this information and thus it was removed. This made first generation implants a danger if they turned rogue as they were privy to secrets that the Taelons wished to hide. (Episode: Sandoval's Run)
At some point, the Taelons came to the conclusion that the prisons on Earth which were used to held criminals were only for incarceration and did not heal the murderers inside. Thus, they planned on a project where they secretly implanted CVI's in these subjects in order to remove their violent impulses. One of the subjects of the program was James Pike who possessed his implant for two years with the motivational imperative to love mankind. He had, however, bonded to his implant on such a level that he had adapted it for further needs on an unconscious level allowing him increased pain threshold, controlling his own vital signs and even understand the Taelon language. He later forced a Human doctor who specialized in CVI implantation to alter his own in order to allow him to
make use of a Skrill implant. (Episode: Avatar)
The Liberation movement managed to get a sample of the cyber virus which they re-engineered with its motivational programming removed allowing the agent to possess freedom of thought. However, they were unusure if the reprogramming was successful and thus tested it on their newly recruited agent William Boone who had been selected as Protector for Da'an. (Episode: Decision) Ronald Sandoval later taught Boone about the benefits of the cyber virus and how one controlled it in time. (Episode: Truth) However, he later faced a breakdown in his CVI which made him more violent to the Companions and removed his motivational imperative to them until a new implant could be delivered into his brain. (Episode: Sandoval's Run)
Siobhan Beckett's CVI was reprogrammed by the Liberation movement in order to prevent her from remembering the resistance headquarters or the fact that she gave birth to the Human-Kimera hybrid known as Liam Kincaid. (Episode: The First of its Kind)