"This is an unprecedented attack," Steinitz said, indicating that Israel had "deflected 44 million cyber attacks on government websites" since it began a widespread air campaign over Gaza on Wednesday.
"All the attacks were thwarted except for one, which targeted a specific website that was down for six or seven minutes," he said.
The comments from Israel's overseer of Internet security came a day after the Anonymous online activist group claimed downing dozens of websites of state agencies and a top bank in protest over the Jewish state's deadly air assault.
It also coincides with both Israeli and Palestinian attempts to exploit the social networks to win over public opinion amid the worst outbreak of Middle East violence in four years.
Steinitz did not say who was responsible. But he said the government had fended off almost every attack, with analysts pointing out that the Jewish state has sophisticated protection that shields its online assets.
Anonymous yesterday claimed it had downed or erased the databases of nearly 700 Israeli sites that included the powerful Bank of Jerusalem finance house. It also claimed to have briefly downed the foreign ministry website in protest over an alleged Israeli threat to cut Gaza's Internet access.