An Army spokeswoman says the information includes names, birth dates, Social Security numbers, addresses and salaries.
The breach was discovered this month.
The commands believed to be affected include Communications-Electronics Command, or CECOM, and Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance, known as C4ISR.
Both were housed at Fort Monmouth up until its closing last year and are now housed at Maryland's Aberdeen Proving Ground.
The Army tells The Asbury Park Press the databases that were breached contained information taken from former Fort Monmouth visitor logs as well as CECOM personnel files.
Information from: Asbury Park Press, http://www.app.com