The foreign man who came to Malaysia in August on the pretext of furthering his studies in computer science and forensic computing was detained on Sept 15 by Bukit Aman's Special Branch Counter Terrorism officers.
Inspector-General of Police Tan Sri Khalid Abu Bakar said the suspect was in communication with top IS leaders in Syria.
"We believe he was trying to hack classified information on American security forces.
"The information will then be channeled back to IS leaders for further action," Khalid said in a statement on Thursday.
The suspect was initially detained under Security Offence (Special Measures) Act (Sosma) 2012 until the police obtained a provisional warrant of arrest issued by the courts.
"He is now being held while waiting for the extradition process to the US to be finalised," Khalid said.
Khalid said the arrest was made possible through cooperation with the Federal Bureau of Investigation (FBI) in combating the threat of IS.