However, North Korean hackers have been suspected to have previously targeted rival South's power grids with wiper malware.
The bombers took off from the US Pacific territory of Guam, before entering South Korean airspace and conducting firing exercises over the East Sea and Yellow Sea, South Korea's military said.
North Korean dictator Kim Jong-Un inspects a military site in North Korea in this undated picture released by state media.
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Trump says he listens to everyone "but ultimately my attitude is the one that matters". Later, the State Department said Tillerson never used "that type of language".
If confirmed, such a hack would be a major blow for South Korea at a time when its relations with North Korea are at a low point.
The joint military drill was the latest show of force against North Korea, whose leader is engaged in a heated war of words with U.S. President Donald Trump.
The exercise showed the "strong ability of the alliance against the North Korean nuclear missile threat", the South Korean air force said.
Russia's TASS news agency quoted North Korean Foreign Minister Ri Yong Ho as saying: "With his bellicose and insane statement at the United Nations, Trump, you can say, has lit the wick of a war against us".
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Ultimately, Postecoglou's blushes were spared as Mooy played Kruse clean through to cross for Cahill's victor . Up stepped Omar al Soma , who hit a rasping shot against the post with Mat Ryan beaten.
The warplanes first conducted a simulated air-to-ground missile drill over the waters east of the Korean Peninsula and then flew over South Korea and conducted the same drill over the waters west of the peninsula, the South Korean military said.
South Korean and US government officials have been raising their guard against more North Korean provocations with the approach of the 72nd anniversary of the founding of North Korea's ruling party, which fell on Tuesday. Lee, who didn't specify his sources, said the plans allegedly stolen by the North include operations for tracking the movement of the North's leadership, isolating their hideouts, executing air assaults and follow-up actions for securing and eliminating targets, which would obviously include North Korean leader Kim Jong Un.
Seoul says North Korea has repeatedly staged cyberattacks on South Korean business and government websites. He revealed that around 235 gigabytes of military documents had been stolen from the Defence Integrated Data Centre, and that 80% of them have yet to be identified.
The training was part of a programme of "extended deterrence" against North Korea, it added.
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White supremacists beat Black schoolteacher DeAndre Harris in a parking garage in Charlottesville on August 12, 2017 . He suffered a concussion, a gash on his head that required almost a dozen staples, and other injuries.