ZID Controller reported a fixed RADAR target generated shadowed code and altitude information to nearby aircraft resulted in false conflict alerts with unreliable RADAR information.

Narrative

I assumed the radar position at FLM/DAC (83/93) sectors around XA:30 local time. I was briefed that the radar scope had picked up a random target about 40 miles NW of the AZQ VOR. For the next hour; every aircraft within roughly a 20 mile radius of that position had a Mode C intruder alert and subsequent targets within 10 miles of the aircraft's position that depicted a squawk code and altitude readout identical to the correlated aircraft I was talking to. On several occasions the target initiated conflict alert to go off with the aircraft who shared the target's code. I asked one of the aircraft if they saw anything where the target appeared or if they saw anything on TCAS and they said that they did not. Management was notified and we staffed a D-side at the position to manually record any Mode C intruder targets generated. We also tried switching from the active to backup radar channel; as well as moving from one scope to the Front Line Manager (FLM) scope. Neither resolved the issue before I went home for the day around XB:30 local. I think someone needs to look at the radar sites associated with the affected area.