After gaining access to On Q systems via vendor software, unknown parties were able to obtain and remove client personal information, including Social Security numbers.

The report seeks to help banks "disrupt rapidly evolving AI-driven fraud," according to Treasury's Nellie Liang. The report found banks have difficulties accounting for AI risks.

Some vendors can act as backups when a cyberattack knocks the regular provider's system offline. Others offer vendor management expertise that may help.

Keeping vendor arrangements under wraps, "pen-tests" and a few simple email setting changes can make a world of difference in avoiding future attacks, experts say.

Malicious actors could be utilizing the same software that cybersecurity experts use to test a company's systems for vulnerabilities.

An unnamed hacker in December "potentially removed" sensitive consumer data including Social Security numbers from the wholesale lender.

The attack is one of three major incidents the lender has suffered in the past three years.

The government mortgage-backed securities guarantor needs data breaches reported within a certain period of time and has specific instructions for subservicers.

The root cause of the hack affecting over 5 million customers was an employee clicking on a link in a work-related search result, according to public case documents.

The mortgage lender said the hack was caused by a third-party's vulnerability.