For example, researchers at Kaspersky Lab tracked the working hours of Duqu’s operators and found they coincided with Jerusalem local time. They also noted that Duqu’s programmers were not active between sundown on Fridays and sundown on Saturdays, a time that coincides with the Sabbath when observant Jews typically refrain from secular work.

Intelligence and military experts have said that Stuxnet was first tested at Dimona, an Israeli complex widely believed to be the headquarters of Israel’s atomic weapons program…

Flame also shares a quirkier trait with Duqu: an affection for American movie characters. Flame’s command for communicating with Bluetooth-enabled devices is “Beetlejuice.” An e-mail that infected an unnamed company with Duqu last year was sent by a “Mr. Jason B.” — which researchers believe is a reference to Jason Bourne of the Robert Ludlum spy tales.