My main thought is the possibility of it being Leonardo. Very thin odds that it's Puck, as MCT has him stapled down tight behind many layers of extremely tight jamming.
Another thought refers back to 10 JackPointers. In that file, it is mentioned that there is someone among the JackPointers that was acting as an inside source for Horizon (the in-game source of the file).
Also, on one of the recent intro splash pages (JackPoint log-on screen), there is a notice from Fastjack that he zapped a sprite that had been parked in the system to track JackPoint. So perhaps the sprite and A. Nonymous are connected (this wouldn't rule out Leonardo, as iirc he has long shown the ability to perform matrix work without hardware).