Per the complaint, with my notes in brackets:

Project Sparta [breach tooling team] was kept separate from Project Sierra [breach action team] to limit the number of people who knew that Equifax itself had been breached. Those Equifax employees who were only part of Project Sparta were not told that Equifax had been breached, but were instead told that they were working for an unnamed client that had experienced a large data breach [...]

https://www.sec.gov/litigation/complaints/2018/comp-pr2018-4...