At least three US oil companies were victims of highly targeted, email-borne attacks designed to siphon valuable data from their corporate networks and send it abroad, according to a published report citing unnamed people and government documents.

The attacks against Marathon Oil, ExxonMobil, and ConocoPhillips began with emails sent to senior executives that included links to booby-trapped websites, according to the report in The Christian Science Monitor. The breaches focused on the companies’ proprietary “bid data” detailing the quantity, value, and location of petroleum discoveries worldwide. The report said at least some of the attacks appeared to originate in China, but didn’t provide proof beyond the existence of servers located in that country used to store some of the stolen data.

“What these guys [corporate officials] don’t realize, because nobody tells them, is that a major foreign intelligence agency has taken control of major portions of their network,” a person said to be familiar with the attacks was quoted as saying. “You can’t get rid of this attacker very easily. It doesn’t work like a normal virus. We’ve never seen anything this clever, this tenacious.”

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