Iran over its nuclear program have come and gone for years. In recent weeks such talk has intensified, though it's still anybody's guess as to whether Israel or the United States might openly carry out military action any time soon. But most experts agree on one thing: A covert war with Iran has already been raging for years. Details are often murky, but the conflict has been punctuated with brazen assassinations, exploding missile sites, crippling cyberattacks, and a litany of arrests and spying allegations on all sides. Below is a timeline of major developments in the war—or at least the ones that are publicly known.

A series of CIA memos describes how Israeli Mossad agents posed as American spies to recruit members of the terrorist organization Jundallah to fight their covert war against Iran. ... A spate of stories in 2007 and 2008, including a report by ABC News and a New Yorker article, suggested that the United States was offering covert support to Jundallah. The issue has now returned to the spotlight with the string of assassinations of Iranian nuclear scientists and has outraged serving and retired intelligence officers who fear that Israeli operations are endangering American lives.

Last summer, the world’s top software-security experts were panicked by the discovery of a drone-like computer virus, radically different from and far more sophisticated than any they’d seen. The race was on to figure out its payload, its purpose, and who was behind it. As the world now knows, the Stuxnet worm appears to have attacked Iran’s nuclear program. And, as Michael Joseph Gross reports, while its source remains something of a mystery, Stuxnet is the new face of 21st-century warfare: invisible, anonymous, and devastating.