Israeli security agencies are on alert over the potential for cyber-attacks by Anonymous on Thursday, after the hacker group previously targeted the Jewish state each April 7.

The attacks in solidarity with the Palestinians have in the past succeeded in blocking government sites, including for the ministries of defense and foreign affairs, but have fallen short of hackers' bombastic declarations to down the Israeli internet altogether.

"We are prepared for all forms of aggression," an official from the Shin Bet domestic security agency told AFP. "Israel is well-protected."

In the past Israeli governmental and company sites have been shut down; sites have been hijacked to display photos and videos from Anonymous; and data has been pirated and made public, said Meni Barzilai from the University of Tel Aviv's cyber research center.

Dozens of experts from both the private and public sectors as well as hackers are to gather Thursday in Tel Aviv to monitor potential attacks and offer help to companies and institutions targeted.

With Israel presenting itself as a leader in cyber-security, the stakes in fending off such attacks are particularly high.

Cyber-security exports reached $6 billion in 2014, amounting to eight percent of a global market estimated at $72 billion.

Some 430 companies specialize in the sector in Israel, compared to 250 a decade ago, employing 19,000 people.

The April 7 cyber-attacks were first launched in 2013 and that year timed to coincide with the eve of Holocaust Remembrance Day in the Jewish calendar.

AFP contributed to this report.