Eugene Kaspersky, whose lab discovered the Flame virus that has attacked computers in Iran and elsewhere in the Middle East, said on Wednesday only a global effort could stop a new era of "cyber terrorism".
"It's not cyber war, it's cyber terrorism and I'm afraid it's just the beginning of the game ... I'm afraid it will be the end of the world as we know it," Kaspersky told reporters at a Tel Aviv University cyber security conference.
"I'm scared, believe me," he said.
News of the Flame virus surfaced last week. Researchers said technical evidence suggests it was built for the same nation or nations that commissioned the Stuxnet worm that attacked Iran's nuclear program in 2010.
In recent months US officials have become more open about the work of the United States and Israel on Stuxnet, which targeted Iran's Natanz nuclear enrichment facility.
The West suspects Iran is developing atomic weapons. Tehran denies this, says it is enriching uranium only for civilian use.
Security experts say Flame is one of the most sophisticated pieces of malicious software so far discovered. They are still investigating the virus, which they believe was released specifically to infect computers in Iran and across the Middle East.
Kaspersky named the United States, Britain, Israel, China, Russia and possibly India, Japan and Romania as countries with the ability to develop such software, but stopped short of saying which nation he thought was behind Flame.
When asked whether Israel was part of the solution or part of the problem regarding cyber war, Kaspersky said: "Both."
"Flame is extremely complicated but I think many countries can do the same or very similar, even countries that don't have enough of the expertise at the moment. They can employ engineers or kidnap them, or employ 'hacktivists'," he said.
Kaspersky said governments must cooperate to stop such attacks, as they have done with nuclear, biological and chemical weapons. Operating systems must be redesigned, he added.
"Software that manages industrial systems or transportation or power grids or air traffic, they must be based on secure operating systems. Forget about Microsoft, Linux, Unix."
Kaspersky said malware like Flame and Stuxnet have a limited lifetime and said undiscovered viruses could be out there.
"It's quite logical that there are new cyber weapons designed and maybe there are computers which are infected."