(Reuters) - Dire warnings from Washington about a "cyber Pearl Harbor" envision a single surprise strike from a formidable enemy that could destroy power plants nationwide, disable the financial system or cripple the U.S. government.
But those on the front lines say it isn't all about protecting U.S. government and corporate networks from a single sudden attack. They report fending off many intrusions at once from perhaps dozens of countries, plus well-funded electronic guerrillas and skilled criminals.
Security officers and their consultants say they are overwhelmed. The attacks are not only from China, which Washington has long accused of spying on U.S. companies, many emanate from Russia, Eastern Europe, the Middle East, and Western countries. Perpetrators range from elite military units to organized criminal rings to activist teenagers.
"They outspend us and they outman us in almost every way," said Dell Inc's chief security officer, John McClurg.
The big fear is that one day a major company or government agency will face a severe and very costly disruption to their business when hackers steal or damage critical data, sabotage infrastructure or destroy consumers' confidence in the safety of their information.
Elite security firm Mandiant Corp on Monday published a 74-page report that accused a unit of the Chinese army of stealing data from more than 100 companies. While China immediately denied the allegations, Mandiant and other security experts say the hacker group is just one of more than 20 with origins in China.
Chinese hackers tend to take aim at the largest corporations and most innovative technology companies, using trick emails that appear to come from trusted colleagues but bear attachments tainted with viruses, spyware and other malicious software, according to Western cyber investigators.
Eastern European criminal rings, meanwhile, use "drive-by downloads" to corrupt popular websites, such as NBC.com last week, to infect visitors. Though the malicious programs vary, they often include software for recording keystrokes as computer users enter financial account passwords.
Others getting into the game include activists in the style of the loosely associated group known as Anonymous, who favor denial-of-service attacks that temporarily block websites from view and automated searches for common vulnerabilities that give them a way in to access to corporate information.
An increasing number of countries are sponsoring cyber weapons and electronic spying programs, law enforcement officials said. The reported involvement of the United States in the production of electronic worms including Stuxnet, which hurt Iran's uranium enrichment program, is viewed as among the most successful.
Iran has also been blamed for a series of unusually effective denial-of-service attacks against major U.S. banks in the past six months that blocked their online banking sites. Iran is suspected of penetrating at least one U.S. oil company, two people familiar with the ongoing investigation told Reuters.
"There is a battle looming in any direction you look," said Jeff Moss, the chief information security officer of ICANN, a group that manages some of the Internet's key infrastructure.
"Everybody's personal objectives go by the wayside when there is just fire after fire," said Moss, who also advises the U.S. Department of Homeland Security.
Industry veterans say the growth in the number of hackers, the software tools available to them, and the thriving economic underground serving them have made any computer network connected to the Internet impossible to defend flawlessly.