Kaspersky Lab has discovered a hacking attempt which tried to sneak sensitive intelligence out of 20 European countries.
A statement from Kaspersky said that the attacks were a complex online assault rarely seen since the turn of the millennium.
Dubbed "MiniDuke" by researchers, malware has infected government computers in an attempt to steal geopolitical intelligence.
Governments targeted include those of Ireland, Romania, Portugal, Belgium and the Czech Republic. The malware compromised the computers of a prominent research foundation in Hungary, and two thinktanks.
Kaspersky told the Guardian the attackers had servers based in Panama and Turkey but looking at the code did not indicate where the attack had come from,
Eugene Kaspersky, founder and chief executive of Kaspersky, said MiniDuke had the potential to be "extremely dangerous" because it was an "elite, old-school" attack that used some 21st century tricks.
He said that it was an unusual cyber-attack and similar to the malicious programming from the end of the 1990s and the beginning of the 2000s.
Kaspersky wondered if these types of malware writers, who have been in hibernation for more than a decade, have suddenly awoken and joined the sophisticated group of threat actors active in the cyber world.