(MSNBC.MSN) — Security experts have discovered a new data-stealing virus dubbed “Flame” they say has lurked inside thousands of computers across the Middle East for as long as five years as part of a sophisticated cyber warfare campaign.

It is the most complex piece of malicious software discovered to date, said Kaspersky Lab security senior researcher Roel Schouwenberg, whose company discovered the virus. The results of the Lab’s work were made available on Monday.

Schouwenberg said he did not know who built Flame.

If the Lab’s analysis is correct, Flame could be the third major cyber weapon uncovered after the Stuxnet virus that attacked Iran’s nuclear program in 2010, and its data-stealing cousin Duqu, named after the Star Wars villain.

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