Three luxury hotels's systems that connect to their computers, phones, and elevators were hacked by a sophisticated virus, according to Kaspersky Lab, a company that sells digital security tools.
All of the hotels played host to diplomatic negotations about Iran's nuclear program. A search of "thousands" of other hotels by Kapersky Labs found no other victims of hacking.
The story was broken by the Wall Street Journal today, which reports:

"Among the possibilities, the researchers say, the intruders might have been able to eavesdrop on conversations and steal electronic files by commandeering and alarms, allowing them to turn them on and off at will to collect information."
The WSJ reports that the virus contained “modules” for taking over electronic systems:

"One module was designed to compress video feeds, possibly from hotel surveillance cameras. Other modules targeted communications, from phones to Wi-Fi networks. The attackers would know who was connected to the infected systems, allowing them to eavesdrop on conversations and steal electronic files.
The virus could also enable them to operate two-way microphones in hotel elevators, computers and alarm systems.
In addition, the hackers appeared to penetrate front-desk computers. That could have allowed them to figure out the room numbers of specific delegation members."
The hotels have not been identified, and none have come forward to admit they have been hacked. Many hotels participated in the talks, as the WSJ notes, including

"the Beau-Rivage Palace in Lausanne, Switzerland, the Intercontinental in Geneva, the Palais Coburg in Vienna, the Hotel President Wilson in Geneva, the Hotel Bayerischer Hof in Munich and Royal Plaza Montreux in Montreux, Switzerland."
The full, sensational story is at the WSJ.
The full report on the technical nature of the virus, not on the hotels, from Kapersky Lab is also online.
MORE TECHNICAL ADVICE: "The Australian Signals Directorate Top35 list of mitigation strategies shows us that at least 85% of intrusions could have been mitigated by following the top four mitigation strategies together."
NB: Image of hotel spying, via Shutterstock.