Credit reference agencies are already prone to false data, and that's without anyone trying to game them.
When I checked this year, 2 out of the 3 major CRAs in my country (Equifax, Experian) had:
- An incorrect flag saying I was not registered to vote, and a note saying this significantly affected my credit rating.
- A bogus address that didn't correspond to any physical location. Nor did it correspond with any address used by any business, that I know of. (If it does, they won't be able to mail me!)
- Three credit application searches (hard searches) in 3 days, for applications I didn't make. (I complained to the relevant company, who agreed they were added due to software errors on their side, and "resolved" the complaint by agreeing to remove them; but in the end they didn't remove them, so my history has unremovable entries for applications I've never made.)
- An account with the largest telecoms provider (BT) in the country that I didn't have (I'd left them 2 years earlier, account fully closed and settled).
- Fictitious monthly entries on the above account showing new amounts being added each month, of seemingly random amounts (no obvious pattern), and flagged as severe, overdue, late payer etc. Not a good look on a credit record, and entirely fictitious. (Fixing this proved arduous, and I ended up having to use three companies in a daisy-chain of each one passing along a formal complaint to the next. I later learned from BT customer support that BT does this to other former customers without their knowledge as well, so for ethical reasons if I can muster the energy I'll be complaining about this to the government regulator)
I could say so much more about the complaints process, terrible customer service in every conceivable way from Equifax specifically, and more, but it would be rather off-topic.
Remarkably, just complaining about the above caused the errors to be acknowledged and correct data found magically by the companies involved, without me needing to provide replacement data. It's as if the companies involved had all the data they needed already, they just aren't using it until a customer finds out and complains.