A group of computer hackers known as ‘Nightmare’ managed to shut down the websites of the Tel Aviv Stock Exchange, as well as the Israeli national airline El Al on Sunday night.According to a spokesperson for the Tel Aviv Stock Exchange, trading was not affected by the hacker attack that shut down the website that provides information regarding the Stock Exchange.

The anonymous hacker group sent an email to the Israeli news website Yedioth Ahranoth, from the same email address that claimed credit for releasing thousands of Israeli credit card numbers. The news agency identified the sender as a Saudi Arabian hacker, but were unable to identify other than the country of origin.

The hack comes one day after representatives of the Hamas party in Gaza issued a statement calling for an increase in cyber-attacks on Israeli targets.

Although the Israeli government bills the country as one of the world’s savviest in the field of computer technology, numerous Israeli companies, agencies and government departments have shown themselves to be vulnerable to attacks by hackers in recent months.

The Israeli government formed a cyber-warfare team in August of last year, intending to address the issue of cyber-warfare, but it is not possible to know the extent which this team have prevented further infiltration, or if they made any impact at all.

In a statement to the press after Sunday night’s attacks, the Israeli Minister of Intelligence and Atomic Energy, Dan Meridor, stated that “This battlefield is not limited by borders, it is fought behind the scenes. You can’t see it and blood isn’t spilled, but there is a battle in new and developing worlds.”

Prior to the attack Sunday night, the most recent hack attack against the Israeli government was last week, and was carried out by a group calling itself “The Gaza Hack Team”. That attack targeted the website of Danny Ayalon, Israel’s Deputy Foreign Minister.