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"We see this as an ongoing process," said ADL Webmaster David Hoffman. "We're trying to stay ahead of the hackers."

Many Jewish organizations have been vigilant in security efforts to prevent hate crimes and vandalism in their offices. That extra effort is now being utilized online, as the organizations see their vulnerabilities in cyberspace.

Phil Baum, the executive director of the American Jewish Congress, said his Web site is less vulnerable because it does not deal with credit card numbers online.

"We are immune from this kind of attack because there is no incentive" to hack, Baum said. AJCongress has notified its server provider of the attack.

Hoffman said the ADL contacted AIPAC to find out how the attack happened, in hopes of learning how to prevent a similar invasion.

"There are fundamental differences in the way we approach" Web sites, Hoffman said. "We think we've come up with a good and secure solution."

AIPAC spokesman Ken Bricker said the organization's site would stay down until they can establish new security measures. The hackers were able to access two databases — one that contained an e-mail list of people who receive daily news items and another that contained credit card information of people who had recently registered with AIPAC online.

"We need to determine just how useful the Web is," Bricker said.

The organization will investigate Internet security to determine whether to continue asking for credit card numbers online.

Although Jewish organizations are awakened to the possibility of online attack, Baum said the fear would not cause them to shut their virtual homes down.

The hackers are "not going to scare us into taking down our Web site," Baum said. "It would be giving them a credit they don't deserve."

Web sites for the Israeli government and Israel Defense Force were targeted by hackers in the past couple of weeks.

In some instances, access to Internet providers whose servers host the sites was disrupted, while in other cases, the assault caused the sites themselves to crash.