The discovery was made during a routine monitoring session that detected unusual network activity. An investigation into the hack is already underway.
"We are notifying individuals whose information may have been compromised," said Rebecca Mills, vice president for student life. "UNLV is working closely with the FBI and other agencies to investigate the incident and protect those who may have been affected."
Reports suggest the hacker is not a former student. All those affected have been informed via email.
The news arrives as part of a swathe of hacking incidents within US educational establishments. Yesterday SC reported a hacker had gained access to the personal information of 120,000 Boston College alumni.
Universities are traditional targets for hackers, in the early days of computing their networks were being attacked in an attempt to steal information. Cliff Stoll's bestseller The Cuckoo's Egg details how a hacker attempted to gain military information by piggybacking on Berkeley's network in the mid-eighties.