The Wall Street Journal reports: When a cybersecurity firm discovered it had been hacked last year by a virus widely believed to be used by Israeli spies, it wanted to know who else was on the hit list.

The Moscow-based firm, Kaspersky Lab ZAO, checked millions of computers world-wide and three luxury European hotels popped up. The other hotels tested—thousands in all—were clean. Researchers at the firm weren’t sure what to make of the results. Then they realized what the three hotels had in common.

Each was infiltrated by the virus before hosting high-stakes negotiations between Iran and world powers over curtailing Tehran’s nuclear program.

The spyware, the firm has now concluded, was an improved version of Duqu, a virus first identified by cybersecurity experts in 2011, according to a Kaspersky report and outside security experts. Current and former U.S. officials and many cybersecurity experts say they believe Duqu was designed to carry out Israel’s most sensitive intelligence collection. [Continue reading…]