WASHINGTON – The White House is acknowledging an attempt to infiltrate its computer system, but says it thwarted the effort and that no classified networks were threatened.

White House spokesman Jay Carney told reporters the White House is equipped with mitigation measures that identified the attack, isolated it and prevented its spread.

He said there was no indication that any data was removed.

“There are distinctions between those networks that contain classified information and those that don’t, and the attack was against an unclassified network,” Carney said.

Carney described the attack as “spear-phishing” and said such efforts against government computer systems are “not infrequent.” Carney spoke in Henderson, Nev., where President Barack Obama is preparing for his first debate against rival Mitt Romney on Wednesday.

“Phishing” is a tactic that involves sending an email that falsely claims to be from a legitimate enterprise in an attempt to trick the user into turning over information.