The Israeli government has said it considers the theft of its citizens' banking information by hackers an act of terrorism and has threatened direct action against those involved.
The hacker, known as "0xOmar" and originally thought to be from Saudi Arabia, revealed the attack had been carried out last week and claimed that 400,000 card details were compromised.
Banks in Israel downplayed this though, claiming only around 15,000 customers were affected.
In response, deputy foreign minister Danny Ayalon said the government considered the attacks to be, "a breach of sovereignty comparable to a terrorist operation", and said the nation would react as necessary.
"Israel has active capabilities for striking at those who are trying to harm it and no agency or hacker will be immune from retaliatory action," he said in widely reported comments.
He added that the government was considering whether the attack was carried out by a rival nation or organisation, as it appeared, "more organised and sophisticated ...than a lone youth".
Elsewhere, reports on Reuters suggest the hacker who claimed responsibility for the attack has been identified as a citizen of the United Arab Emirates based in Mexico.
The attack on Israel last week was one of several high-profile incidents, with Symantec forced to concede some of its Norton AntiVirus source code was hacked, allegedly from servers used by the Indian military, while Anonymous hacked the Sony Pictures site.
Israel has itself been accused of carrying out cyber attacks in the past, in particular the Stuxnet attack on nuclear facilities in Iran, in an attempt to disrupt that country's nuclear programme.
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