A day after a technical glitch brought down the Cellcom mobile network across the country, a system-security expert said it could have been subjected to a cyber attack.

"I tend to believe a fundamental malfunction like that was caused by sabotage," said Boaz Dolev, a former manager of the Israel Government Portal who today owns a consultancy for information security.

Dolev said yesterday the malfunction in Cellcom's computer system on Wednesday had the characteristics of a Zero-Day attack, which reboots the computers and crashes their operating system.

"We haven't seen such malfunctions [as the one that took place in Cellcom] in the world and I think it was unique," Dolev said. "A Zero-Day attack could certainly cause such a breakdown."

Like similar companies whose services are based on complex computer systems, Cellcom invests considerable resources in safeguarding its computers from electronic attacks and penetration.

Companies generally fear their systems will be hacked into for economic and industrial espionage. In recent years there have been growing fears that hostile organizations and states would attempt to hack into Israeli technological systems to disrupt life in the country for political reasons.

The state authority for safeguarding information in the Shin Bet security services is in charge of protecting the government's computer systems and vital national infrastructure systems.

The authority instructs the bodies subjected to it how to protect their technological systems from cyber attacks.

Companies like Bezeq, which are categorized as national infrastructure, are instructed by the Shin Bet on safeguarding their systems. Private communication companies providing mobile phone and Internet services are responsible for their own security.