"The rival side has the ability to do it," Erez Kreiner -- who founded the National Information Security Authority in 2002, Israel's first cyber-defense unit in the Shin Bet -- told Haaretz.
"There are constant attempts to hack Israel's critical system, some study them some attack them," he said.
"A country can be hiding behind someone who looks like an individual hacker. As a defender, you have to take into consideration that someone may have penetrated your system six months ago and is waiting to attack when it suits him. And in contrast to physical warfare, the hacker on the other side has almost no risk of paying a price," he added.
Kreiner -- who left the unit in 2012 and is now chief executive officer for an independent consulting company on cyber defense -- said that in the past year, Israel has experienced a number of attacks that led to a denial of service. Some government ministries and the Bank of Israel were among the sites targeted, he said.
While such attacks created public panic, they failed to cause damage to the State of Israel, he said. The potential of a pinpoint attack that falls under the radar is of far more concern, he added.
"The ability to harm us is there. It's just a matter of making the decision."
He described Israel's protection system as "reasonably good," but stressed that while Israel remains a leader in the cyber realm, it does not have the extensive resources open to other countries.
"The difference between us and them is between a speedboat and an aircraft carrier. We respond faster," he said.