A group of online hackers called on the world’s “cyber warriors” to attack Israeli websites on Monday, in a repeat of last year’s efforts by the same group to disrupt the activities of national institutions.

The Anonymous collective issued a rallying cry on its YouTube account, saying: “We call upon our brothers and sisters to hack, deface, hijack, database leak, admin takeover, and DNS terminate the Israeli Cyberspace by any means necessary.”

On the same date last year the website of Yad Vashem, the Prime Minister’s Office and the Israel Defense Forces were attacked, with limited success. Since then, over a dozen Defence Ministry computers have been hacked and temporarily taken over.