WASHINGTON — If President Obama adopts the most far-reaching recommendations of the advisory group he set up to rein in the National Security Agency, much would change underneath the giant antennas that sprout over Fort Meade, Md., where America’s electronic spies and cyberwarriors have operated with an unprecedented amount of freedom since the Sept. 11, 2001, attacks.

No longer would a team of two dozen or so agency analysts be able to type into a computer that there was a “reasonable, articulable suspicion” about the person behind an American telephone number and, in seconds, see every call made to and from that phone — followed by the same records for hundreds or thousands of their contacts. Instead, an individual court order would have to be obtained — a far slower process that, just months ago, Mr. Obama’s intelligence team insisted would be too cumbersome in halting attacks.

On the same guarded campus, military and civilian computer hackers working for the United States Cyber Command would be barred from using one of the most important building blocks of their growing arsenal of sophisticated cyberweapons. Every day they exploit previously unknown flaws in computer programs, known in the industry as “zero-days,” to conduct both surveillance and attacks. A handful of such flaws — named for the fact that they have been known to the world for zero days, and thus cannot be defended against — were central to attacking Iran’s nuclear plant at Natanz.

Already, critics of the advisory report have called it a form of unilateral disarmament.

“Bad idea,” said James Lewis, the cyberexpert at the Center for Strategic and International Studies in Washington. “We’d be the only country in the world to knock ourselves out of the market — the Chinese, the Russians, the Iranians, every criminal gang would still be out there developing attacks” with these flaws.