Cyber attacks by rogue nations will spread: security experts WASHINGTON: Another suspected North Korean computer attack on South Korea dramatises the mounting threat that rogue nations such as North Korea and Iran will stage disruptive, hit-and-run cyber attacks on the United States, independent security experts warned Congress on Wednesday. Pyongyang's alleged onslaught on Wednesday interrupted service at four South Korean banks and shut down computers at three broadcast networks. The attack came during a bitter war of words between the countries over North Korean missile tests and an underground nuclear explosion, which provoked international condemnation. Nations such as North Korea and Iran periodically resort to deniable, pinprick "demonstration" attacks against more powerful nations such as the United States to symbolically retaliate against US-led sanctions, cyber-specialists told the panel within the House Committee on Homeland Security that handles cybersecurity. Despite the showcase attacks, the two nations pose less of a threat to computer networks and data in the United States than China and Russia, which routinely disrupt US financial institutions, steal corporate trade secrets or try to penetrate military networks, the experts said. Yet North Korea remains a "wild card" because it has both growing capabilities for cyber strikes and a willingness to use them, said Frank J. Cilluffo, a former White House official in the Obama administration who now serves as co-director of the Cyber Center for National and Economic Security at George Washington University. "We're never going to firewall our way out of this problem," Mr Cilluffo said. We need to improve our capabilities to the point where we can deter, persuade and compel. North Korea's capabilities "should not be underestimated," said Republican Patrick Meehan, chairman of the panel hearing experts' testimony. In addition to Wednesday's attack, Pyongyang has carried out at least two other so-called denial-of-service attacks in the past four years, according to the anti-virus company McAfee. A 2009 attack crashed some US government websites. A 2011 attack disrupted South Korean government and banking sites. Iran has staged sneak attacks on both the United States and Saudi Arabia in recent months in response to crippling UN-backed economic sanctions imposed because of Iran's alleged quest for nuclear weapons. Attacks have targeted American financial institutions such as Bank of America, PNC Financial Services Group, Sun Trust Banks Incorporated and BB&T Corporation, as well as JP Morgan Chase. Last summer, Iran allegedly carried out a cyber-attack on the Saudi national oil company Aramco that damaged an estimated 30,000 computers. Republican Michael McCaul, chairman of the entire House Committee on Homeland Security, said Iran's readiness to use its offensive cyber capability raises the most concern. China and Russia want to disrupt operations or steal secrets, said Mr McCaul, a former counterterrorism official with the Justice Department. But "Iran has the capability to destroy," Mr McCaul declared. They're red-lining us, testing us - how far can they go before we ultimately respond? Ilan Berman, a former adviser to the Pentagon and the CIA now with the American Foreign Policy Council, said Iran has developed significant offensive capabilities for cyber attacks. The arsenal is being used to "demonstrate that they have the capability to reach out and touch the United States and its allies in the event of conflict," said Professor Berman, a member of the conservative "Committee on the Present Danger." Iran is building a cyber capability that is "retaliatory," Professor Berman testified. Countries that wage cyber attacks such as China and Russia are simultaneously "pursuing diplomatic normalcy" he said. Iran is not. Iran is expecting a catastrophic breakdown of relations with the west.