Ryan Cleary, 19, appeared at a London court charged with offenses including hacking into the website of the Serious Organised Crime Agency (SOCA), the British equivalent of the FBI.
Judge Nicholas Evans initially granted him bail after his defense team said the teenager had been diagnosed with Asperger's syndrome, a form of autism, since his arrest.
However the decision was swiftly overturned after objections by prosecutors. His bail appeal will be heard on Monday.
Police arrested Cleary on Monday last week at his home in Wickford, southeast England, as part of a probe by Scotland Yard and the FBI into the Lulz Security hacking group.
Lulz has claimed responsibility for a month-long rampage against international businesses and government agencies, including the CIA and Senate in the United States and electronics giant Sony.
Cleary was in court for the second time in three days. He did not enter any plea to the five offences under the Criminal Law and Computer Misuse Act with which he is charged,