Computer systems across the world are attacked by a ransomware, which bore similarities to a recent assault that crippled millions of network.
Many companies in Russia, United States, and across the globe are reporting that their It systems are being disrupted as a result of the cyber attack.
British advertising agency WPP, Ukrainian firms, including the state power company and Kiev's main airport, were among the first to report about the issue.
The Ukrainian's Nuclear Power Plant, Chernobyl, had to switch manual checking of radiation level after its Window-based sensors were affected by a cyber attack.
According to the Experts, the malware is exploiting the same weaknesses that were used by the WannaCry ransomware attack last month.
"It initially appeared to be a variant of a piece of ransomware that emerged last year," said computer scientist Prof Alan Woodward.
"The ransomware was called Petya and the updated version Petrwrap.
"However, now that's not so clear."
The Russian cyber security firm Kaspersky Lab said that the malware was a "new ransomware that has not been seen before," but it resembles Petya, an old malware.
As a result, the firm named it NotPetya. They reported that it attacks had been detected in Poland, Italy, Germany, France and the US in addition to the UK, Russia, and Ukraine.