The hacker collective Anonymous said it is responsible for taking down some websites and leaking passwords, calling the air war against Palestinians "barbaric, brutal and despicable," CNN reported.
Israel says the cyberattacks largely have been unsuccessful.
But Anonymous posted a list of more than 650 Israel-based websites it says it has knocked down or defaced since the air war began.
"They've knocked down websites, deleted databases and have leaked email addresses and passwords," Casey Chan wrote Friday for the tech site Gizmodo, CNN reported. "It's a whopping takedown."
In a release, Carmela Avner, Israel's chief information officer, said Sunday: "The war is being fought on three fronts. The first is physical, the second is the world of social networks, and the third is cyberattacks.
"The attackers are attempting to harm the accessibility of Israel's government websites on an ongoing basis. When events like the current operation occur, this sector heats up and we see increased activity. Therefore, at this time, defending the governmental computer systems is of invaluable importance."
An Anonymous Twitter feed Monday said another set of hackers had defaced the Israeli versions of several Microsoft websites, including Bing, MSN and Skype, CNN reported.
"Microsoft is aware of the site defacements and working to get all sites fully functional," a company spokeswoman told CNN in an email.