[woodbutcher1963]

Yes, when I did it there were four agencies.

Google AI says:

The four major credit bureaus in the U.S. are
Equifax, Experian, TransUnion, and Innovis.

One required I send them a letter via US mail. They then sent a letter back to keep when I want to unfreeze my credit with the code number.
Their version of multi factor authenticfication

[goodnesswins]

We did innovis online...do not have to join, just freeze...then they sent confirm letter