According to cybersecurity analysts, a data-wiping hacking programme was discovered on hundreds of computers in Ukraine on Wednesday, increasing fears of a devastating cyberattack as the Russian military marched into Ukraine’s rebel territories.

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It was unclear who was behind the hacking incident, which came after a separate intrusion on Ukrainian government websites earlier Wednesday. Wiper virus, which was found on Wednesday, is meant to remove data from computers and render them useless.

“We are aware of multiple commercial and government organizations in Ukraine impacted by the destructive malware today,” said Charles Carmakal, senior vice president and chief technology officer for cybersecurity firm Mandiant, CNN reported.

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CNN also stated that according to Vikram Thakur, technical director of Broadcom’s cybersecurity unit Symantec, the intrusion affected at least one Ukrainian financial institution and one Ukrainian government contractor with a presence in Latvia.

According to cybersecurity firm ESET, which has many clients in Ukraine, the malicious code infected “large organisations.” The hacking tool was designed two months ago, but “was deployed only today and we have seen it only in Ukraine,” according to Jean-Ian Boutin, ESET’s head of threat research.

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Russian cyber activities will very certainly be used in tandem with military action in Ukraine, according to US sources. Last week, the White House attributed a different round of cyberattacks on Ukrainian websites to Russia’s military intelligence directorate, the GRU.