The police and FBI thought (or at least told everyone) that AREM was a computer hacker. The man behind the name was Robert Mitchell. He would break into top secret web sites that he could get access to and find information on the latest Andromeda and Novacom workings. He would then pass this incriminating information on to trusted people who could use it in the mission to bring down Novacom's programing.
However, as Mitchell was a Novacom insider, it would never do to just hand out the information in public. So he would also hack into closed systems (such as the one at Whit's End (Connellsville)) under the code name AREM to reveal to people how they were being used.
The name AREM was to hide Mitch's real identity so people such as Bennett Charles could not try to keep him from talking.
However when the FBI thought he had too much information under his belt, they put Mitch in the Witness Protection Program for his own protection. The public world was now too dangerous for Mitchell.
Everyone besides the police called him AREM (air-um) but the police referred to him as AREM (R.M). AREM stands for Robert Mitchell's initials (R.M).