By Ted Bridis
The Associated Press

WASHINGTON - The weekend attack on the Internet crippled some sensitive corporate and government systems, including banking operations and 911 centers, far more seriously than many experts believed possible.

The nation's largest residential mortgage firm, Countrywide Financial Corp., told customers who called Monday it was still suffering from the attack. Its Web site, where customers usually can make payments and check their loans, was closed most of Monday with a note about "emergency maintenance."

Police and fire dispatchers outside Seattle resorted to paper and pencil for hours Saturday after the virus-like attack disrupted operations for the 911 center that serves two suburban police departments and at least 14 fire departments.

American Express Co. confirmed customers couldn't reach its Web site to check credit statements and account balances during parts of the weekend. Perhaps most surprising, the attack prevented many customers of Bank of America Corp., one of the largest U.S. banks, and some large Canadian banks from withdrawing money from automatic teller machines Saturday.

President Bush's No. 2 cyber-security adviser, Howard Schmidt, acknowledged Monday that "collateral damage" stunned even experts who have warned about uncertain effects on the nation's most important electronic systems from mass-scale Internet disruptions.

"One would not have expected a request for bandwidth would have affected the ATM network," he said. "This is one of the things we've been talking about for a long time, getting a handle on interdependencies and cascading effects."

Shouldn't have happened

Miles McNamee, a top official with the technology industry's Internet early-warning center, said the attack was "comparable to the worst of previous denial of service attacks and if so, marks another multibillion-dollar hit to the global Internet community."

The White House and Canadian defense officials confirmed they were investigating how the attack, which started about 12:30 a.m. EST Saturday, could have affected ATM banking and other important networks that should remain immune from traditional Internet outages.

Mr. Schmidt said early reports suggested private ATM networks overlapped with parts of the public Internet. Such design decisions were criticized as "totally brain-dead" by Alex Yuriev of AOY LLC, a Philadelphia consulting firm for banks and telecommunications companies.

Officials were most concerned about risks that citizens might lose confidence in financial networks.

"Their bread and butter is the public being able to get access to their accounts when and where they want them," said Ron Dick of Computer Sciences Corp., former head of the FBI's National Infrastructure Protection Center. The virus-like attack, alternately dubbed "Slammer" or "Sapphire," sought vulnerable computers to infect using a known flaw in popular database software from Microsoft Corp. called "SQL Server 2000." Microsoft said it has sold 1 million copies of the software.

The attacking software scanned for victim computers so randomly and so aggressively that it saturated many of the Internet largest data pipelines, slowing e-mail and Web surfing globally.