YORBA LINDA, Calif. — The U.S. is still probing the extent of a recent cyber leak of what purports to be hacking tools used by the National Security Agency, the nation’s top intelligence official said Wednesday.

“We are still sorting this out,” James Clapper, director of national intelligence, said at an event at the Nixon Presidential Library and Museum in Yorba Linda, California.

“It’s still under investigation,” Clapper said. “We don’t know exactly the full extent — or the understanding — of exactly what happened.”

The tool kit consists of malicious software intended to tamper with firewalls, the electronic defenses protecting computer networks. The leak has set the information security world atwitter — and sent major companies rushing to update their defenses.

The rogue programs appear to date back to 2013 and have whimsical names like EXTRABACON or POLARSNEEZE. Three of them — JETPLOW, FEEDTROUGH and BANANAGLEE — have previously appeared in an NSA compendium of top secret cyber surveillance tools.

The documents have been leaked by a group calling itself the “Shadow Brokers,” although many have floated the possibility of Russian involvement.

CIA Director John Brennan, who appeared with Clapper at the event, called cyber threats the most serious issue facing the nation.

“This administration, the intelligence community is focused like a laser on this and I would say the next administration really needs to take this up early on as probably the most important issue they have to grapple with,” Brennan said.