That'd be Equifax, Experian, and Transunion. You can also freeze your credit at Innovis to get all four.
The freeze will require them to contact you before doing anything. The alert doesn't do much in practice (from the people I know who've had it) - it's just ignored.
This may be the pragmatic approach, but it's also why these companies still exist.
At risk of being too blunt - fuck that shit. I will spend thousands before I give them a dime of my money. I have zero business relationship with them, and I consider such crap absolute extortion. The world is a better place without credit rating agencies. Heck, I remember a point in time where it was questionable whether these companies were even legal to begin with. So far have we fallen.
These are things people should be getting violent about.
I want to avoid giving them money but Equifax handles my W2 for some reason.
Identity thieves prize the W-2 and payroll data held by companies like TALX because they can use it to file fraudulent tax refund requests with the IRS and the states on behalf of victim consumers.
Fraudsters reset customer PINs by answering simple "knowledge-based authentication" questions.
Naturally many of the answers to these questions are in the data leaked by the credit reporting division.
 Fraudsters Exploited Lax Security at Equifax’s TALX Payroll Division https://krebsonsecurity.com/2017/05/fraudsters-exploited-lax...