JERUSALEM -- A loose international coalition of pro-Palestinian computer hackers threatened to carry out what it called "a massive cyberassault" against Israel on Sunday, but the campaign created mostly minor disruptions, and the Israeli government said that as of midday its Web sites were still accessible to the public.
Numerous sites, including some hosted by the government, were briefly closed down or defaced starting on Saturday evening, and some data was stolen, according to Israeli cyberexperts. On Sunday afternoon, the Ministry of Finance said in a statement that government sites were "under DDoS attack," referring to Distributed Denial of Service, a method used by hackers to make sites unavailable, and that Israeli computer experts were working to repel the attacks in cooperation with Internet service providers.
The statement added that the Foreign Affairs Ministry's Web site was inaccessible "for a few seconds before returning to normal operations" and that generally "a slowdown or unavailability of service could be expected from time to time."
The Web site of Yad Vashem, Israel's official Holocaust memorial, was also hit by a cyberattack as Israel was preparing to mark its annual Holocaust Remembrance Day.
Guy Mizrahi of Cyberia, an Israeli cybersecurity firm, said in an interview that the damage was not significant and that most of the attacks were "childish."
The shadowy network of hackers who identified themselves as belonging to the Anonymous collective, along with various allied groups, announced last week that "elite cybersquadrons from around the world" had decided to unite to "disrupt and erase Israel from cyberspace." Among other things, they blamed Israel for violating the November cease-fire in Gaza by carrying out airstrikes, a reference to the assaults on Tuesday on two open areas in northern Gaza that caused no damage or casualties. Israel said the strikes were in response to a renewal of rocket fire into southern Israel.
Israel has been working to protect itself from cyberattacks, establishing a National Cyber Bureau in early 2012 to coordinate computer security efforts.
Isaac Ben Israel of the National Cyber Bureau told Israel Radio on Sunday that Israel "has always been more prepared than other places in the world."
"When we talk about cyberwar we are talking about attacks on water, electricity, infrastructure, but Anonymous does not have that kind of ability," he said. "The fact that we don't have any big damage is not because there are no attacks. We see the attacks, and they are blocked."
Pro-Israeli hackers, some working under the name Israeli Elite Force, said they had retaliated by posting pro-Israeli messages on Web sites in the Muslim world.
The pro-Palestinian hackers called their campaign Operation Israel. Activists logged and tracked their progress through a Twitter account, #OpIsrael.
But some of the sites in Israel that the hackers had claimed to have brought down -- like the ones hosted by Coca-Cola, the prime minister's office and Invest in Israel, an initiative of the Industry, Trade and Labor Ministry, appeared to be working on Sunday.
The pro-Palestinian hackers seemed to have had more success in attacking small businesses and individual Facebook pages. At midday they announced on Twitter that they had defaced the Web site of an Israeli hair salon, Peter Hair, in Ramat Hasharon, near Tel Aviv.
The salon site's home page showed a person with a masked face, an image associated with Anonymous, holding a sign saying "Indonesian Security Down #OP ISRAHELL." The rest of the screen was filled with a message to the government, accusing Israel of having "wronged humanity." The hackers signed off with the message, "We are Muslims, Soldier of Allah."
Reached by telephone on Sunday evening, the owner of the salon, Peter Imseis, said he had not been aware that the site had been hacked and added that it had not affected his business. Asked why he thought the salon had become a target, he said, "I don't have a clue. It's very strange."world
This article originally appeared in The New York Times.