Israeli defense Web sites shut down on Sunday, but the government claimed the hacker collective Anonymous had nothing to do with the system failure.

Official pages for the Israeli military, the Mossad intelligence agency, Shin Bet (Israel Security Agency) and government ministries all went down for hours and didn't go back online until Monday morning.

Israel claimed that the crash was caused by a technical glitch, according to Voice of America, and not by the hackist group increasingly known for its Internet vigilantism.  

Nonetheless, the timing of the shutdown points toward Anonymous, which posted a video message to Israel Friday, threatening to strike back, again and again, if Israel continued to block an international flotilla sending humanitarian aid to Gaza.

That same day, Israel blocked the Gaza Flotilla, as it has come to be known. The government ordered Israel Defense Forces to board three ships, on which 27 international activists were allegedly carrying supplies to be given to Palestinians.

In the video, Anonymous referenced a number of other instances when Israel intercepted the flotilla, which the group claims was in international waters and not in Israel's jurisdiction.

[The activists] were not inside Israeli territories, and are not carrying any weapons... This is a clear sign of piracy on the high seas, Anonymous said in the video.  

Furthermore, U.N. resolution 3005 states, that all resources (so also the sea) and natural wealth falls under the control of residents of Gaza.

As a group, Anonymous recognizes Palestine's statehood, and promised to attack Israel repeatedly until it allows the boats to deliver aid to Gaza.

Your actions are illegal, against democracy, human rights, international, and maritime laws. Justifying war, murder, illegal interception, and pirate-like activities under an illegal cover of defense will not go unnoticed by us or the people of the world, the video continues.

After an investigation, Israeli Internet security officials have labeled the crash on Sunday a coincidence caused by a chain of hardware error.

It's all part of a project called Tehila that puts all of those sites together in one data center, Nitzan Miron, the chief executive of Tel Aviv security company 6Scan, told The Guardian.  When one fell, they all fell. The back-ups failed. Hopefully next time they'll have better back-ups and this kind of thing shouldn't happen. Those were just the front-end sites. They don't contain the actual classified information.

Yet, if the attacks weren't the work of Anonymous -- or simply the work of a computer bug -- others speculate that it could be a retaliation from Palestine. Last Tuesday, hackers shut down the Palestinian Authority's Internet and phone network, slowing down or stopping services for all Palestinians in the West Bank and Gaza Strip.

Palestinian Authority's Telecommunications Minister Mashour Abu Daqqa told Reuters that the attack, which came one day after Palestine won its bid to join UNESCO, was organized by a state.

Israel could be involved as it announced yesterday that it was considering the kind of sanctions it would impose on us, Abu Daqqa told Agence France Presse last week. The Israeli government did not comment.

Friday's video was not the first time that Anonymous has targeted Israel. In the past, the group has threatened to attack the Web site for the Knesset, the legislative body of the Israeli government.

As a result, Israel built the national cybernetic taskforce to protect the country from foreign-born cyber-attacks in May, an essential tool in age where hackers with social agendas are targeting state governments.

Israel is exposed to cyber-attacks which can paralyze entire life systems on which the country runs, Israeli Prime Minister Benjamin Netanyahu said at the time.  

I cannot go into detail about individual attacks, but not because there weren't any. I promise that we will battle any future attacks -- I have no doubt about it.

Earlier this month, Anonymous went on the offensive in Mexico, threatening to reveal local and national authorities who were cooperating with drug cartels.

An Anonymous member was reportedly kidnapped by the powerful criminal organization Los Zetas. Anonymous tried to blackmail members of the cartel, threatening to reveal their identity if the member was not freed.

We can't defend ourselves with a weapon, but if we can do this with their cars, houses, bars, brothels, and everything else in their possession, Anonymous said in a video message similar to the one sent to Israel. It won't be difficult. We all know who they are and where they are.

The kidnapped Anon was released last week and the cyber-attack has been called off, according to Anonymous' unofficial spokesperson, Barrett Brown.

In the past, Anonymous has attacked credit card companies which refused to accept donations for Wikileaks, other businesses, the Pentagon, and tried to take down the German stock exchange.