class="story-body__introduction">Companies across the globe are reporting that they have been struck by a major ransomware cyber-attack, BBC report.British advertising agency WPP is among those to say its IT systems have been disrupted as a consequence. Ukrainian firms, including the state power distributor and Kiev's main airport were among the first to report issues. Experts suggest the malware is taking advantage of the same weaknesses used by the Wannacry attack last month. "It appears to be a variant of a piece of ransomware that emerged last year," said computer scientist Prof Alan Woodward. "It was updated earlier in 2017 by the criminals when certain aspects were defeated. The ransomware was called Petya and the updated version Petrwrap." Andrei Barysevich, a spokesman for security firm Recorded Future, told the BBC that it had seen the malware for sale on many forums over the last 12 months. "It only costs $28 (£22) on the forums," he said. "But we are not sure if they used the latest version or a new variant of it. Mr Barysevich said the attacks would not stop because cyber-thieves found them too lucrative. "A South Korean hosting firm just paid $1m to get their data back and that's a huge incentive," he said. "It's the biggest incentive you could offer to a cyber-criminal." Network down Others reporting problems include the Ukrainian central bank, the aircraft manufacturer Antonov, and two postal services. Russian oil producer Rosneft and Danish shipping company Maersk also say they face disruption, including its offices in the UK and Ireland. "We can confirm that Maersk IT systems are down across multiple sites and business units due to a cyber-attack," the Copenhagen-headquartered firm said via Twitter. "We continue to assess the situation. The safety of our employees, our operations and customers' business is our top priority."