The latest U.S. sanctions on North Korea are "pretty light and symbolic at best," a former CIA director has said, calling for tougher restrictions to make life harder for leaders of the communist regime.

Early this month, the U.S. announced retaliatory sanctions in response to the North's alleged cyber-attack on Sony Pictures, blacklisting three North Korean entities and 10 officials, including the Reconnaissance General Bureau, Pyongyang's top spy agency.

"I think they're pretty light and symbolic at best," former CIA Director Michael Hayden said during a Bipartisan Policy Center forum on cyber-security, comparing the latest measures unfavorably with the 2005 blacklisting of a Macau bank, which almost cut off the North from the international financial system.

The blacklisting of Banco Delta Asia not only froze North Korean money held in the bank but also scared away other financial institutions from dealing with Pyongyang for fear they would also be blacklisted. The measure is considered the most effective U.S. sanction yet on the North.

"Frankly, I was in government when it happened. We were all surprised it worked so well," Hayden said. "When you can turn the torque up on elites for luxury goods and the ability to exchange money you do have an effect on the North Korean regime. Those (latest) sanctions ... are not that."

The U.S. later lifted the BDA sanctions to get Pyongyang back to denuclearization talks.

Former Congressman Mike Rogers also said the latest sanctions were "light at best."

"There is no real financial grind that they are going to go into to impact the people who are living well in North Korea," said Rogers, who served as chairman of the Permanent Select Committee on Intelligence, the primary House committee charged with the oversight of the U.S. intelligence community.

"Most people don't even have electricity. One in 10 have access to electricity and that's not for 24 hours a day. So, if you are going to do this, you have to start impacting the people who are enjoying all of the niceties of life with no consequence," he said during the forum.

Despite such doubts about the latest sanctions, U.S. administration officials have argued that the measures are an "important new tool" that gives a "tremendous amount of flexibility" against those who provide support for the blacklisted North Korean entities and officials.

Meanwhile, John McAfee, founder of anti-virus firm McAfee, said he can say for sure that it is not North Korea that hacked Sony. He claims he has been in touch with the real perpetrators and said the FBI was wrong in blaming the North.

"I can guarantee they are wrong. It has to do with a group of hackers -- I will not name them -- who are civil libertarians and who hate the confinement, the restrictions the music industry and the movie industry has placed on art and so they are behind it," McAfee said, according to IBTimes UK.

Some private cyber-security experts have raised questions about the FBI's finding, claiming the skills employed in the attacks were too sophisticated for the North. They have raised the possibilities that laid-off Sony employees or others might have been behind the attacks.

FBI Director James Comey said at a cyber-security conference last week that he is sure that the North was the perpetrator in the Sony hack. The hackers "got sloppy" several times and revealed IP addresses that were used exclusively by North Korea, he said. (Yonhap)