The closing of the U.S. government might create an ideal environment for cyber terrorists and hackers to attack because agency defenses could be hindered by reduced manpower, the Federal Times reported.

Vital computer operations such as those operated by the Department of Homeland Security remain staffed to provide monitoring and detection services, the Times said.

"That would be suicide to turn that stuff off," said an unnamed chief information security officer (CISO) at one government agency. "We can go to bare bones because the big wall is still up."

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However, the CISO predicted that the longer the shutdown lasts, the more likely it is the government would become a "target of opportunity" for hackers.

Under current conditions, federal agencies are not fully staffed at the technology level to detect obscure events that could mask a bigger problem, he told the Times.

Scott Montgomery, vice president of public sector solutions at McAfee, a security software firm, said one problem is that potential attackers can learn who is vital at the computer security level at U.S. agencies because those personnel are still on duty during the shutdown.

"I might not be attacking them today, but I'm going to learn everything I can because the government told me they are important," Montgomery told the Times.

"I would expect there to be a rise in spear phishing attacks against [those] individuals, [and] that's what we need to be vigilant against."

James Clapper, director of national intelligence, told the Senate Judiciary Committee earlier this month that the government shutdown is dangerous for U.S. security.

The New York Daily News reported Clapper as saying the closure "is a dreamland for foreign intelligence to recruit, especially as our employees, already subject to furloughs driven by sequestration, will have even greater financial challenges."

Gen. Keith Alexander, director of the National Security Agency, said the shutdown "has impacted us very hard."

The Daily News reported Alexander suggested that 70 percent of intelligence employees are furloughed, including over 960 with Ph.D.s, 4,000 computer scientists and 1,000 mathematicians.

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