Russia-based Kaspersky Lab said it found the spyware in three European hotels that hosted negotiations involving Iran and six world powers and also on the company's own computers.
Both Kaspersky and US security company Symantec said the virus shared some programming with previously discovered espionage software called Duqu, which security experts believe to have been developed by Israelis.
Israeli government officials had declined to comment, but on Thursday Deputy Foreign Minister Tzipi Hotovely denied Israel was involved. "The international reports of Israeli involvement in the matter are baseless," she told Army Radio.
"What is much more important is that we prevent a bad agreement where at the end of the day we find ourselves with a Iranian nuclear umbrella," she said.
Israel, widely believed to be the Middle East's only nuclear power, has denounced the diplomatic opening to Iran, saying it doubts any agreement arising from the talks will sufficiently restrain the atomic programme of its arch-enemy.
The West suspects Iran wants to develop a nuclear weapons capability from its enrichment of uranium. Iran says it is seeking nuclear energy for electricity and medical isotopes. — Reuters