In what has been called an "unprecedented criminal action that has nationalist aspects," Internet hackers based in Saudi Arabia published the credit card details of around 14,000 Israelis.
Israeli credit card companies were scrambling on Tuesday to secure the accounts of their customers.
Initially, the perpetrators claimed they had published the details of some 400,000 Israelis.
The first message allegedly posted by the hackers said "We decided to give the world a gift for New Year's -- the personal information of 400,000 Israelis."
"It will be so fun to see 400,000 Israelis stand in line outside banks and offices of credit card companies to complain that their cards had been stolen, to see banks shred 400,000 cards and reissue them, to see that Israeli cards are not accepted around the world, like the Nigerian cards," the hackers said.
The Saudi hackers urged people around the world to use the stolen information for purchases. The cards reportedly belonged to "hard-working Israeli families," one analyst said.
The Jerusalem Post's Yaakov Lapin noted that the hackers had "found one poorly guarded website connected to two online-coupon websites and used it to access a large number of credit card numbers."
Lapin also noted that last year, the Knesset's Science and Technology Committee cautioned that "without tanks, and without planes...it is possible to bring about the collapse of a state, and no military can come to the rescue."
The Jerusalem Post and Ha'aretz contributed to this report.