Computer hacks that cause more mischief than money losses are often prosecuted by U.S. authorities, but long prison sentences are rare.

The takedown of the U.S. Central Intelligence Agency's website is the most recent example of a mischievous kind of hack. There was no immediate evidence that any sensitive data was compromised when the agency's website went down on Wednesday.

U.S. cybercrime laws apply to attacks regardless of whether there have been data breaches, said Ross Nadel, a former federal prosecutor who specialized in investigating computer crimes.

Even if a hacker does not steal information, a victim need only show that he or she suffered $5,000 in damage in a one-year period to trigger prosecution under the Computer Fraud and Abuse Act, he said.

You can get to $5,000 just by hiring a lawyer, said Thomas Nolan, a San Jose, California-based attorney who has defended hackers.

Investigating attacks is always difficult for prosecutors. Rather than directly attack a website, hackers often use intermediary computers that have been previously compromised, Nadel said.

But the hacking of the CIA website will likely get an close look. The government usually prioritizes high dollar crimes -- or those that target government institutions.

Of course if someone is attacked like the CIA, I would assume that is going to be taken very seriously, Nadel said.

Cyber attacks have targeted multinational companies and institutions in recent weeks, including Sony Corp, Citigroup and the International Monetary Fund. Sony faces dozens of lawsuits related to the theft of consumer data from its Playstation network.

The same hacker group that claimed responsibility for the Sony breach, Lulz Security, said it targeted the CIA website.

The government does go after hackers who do not exact a high financial cost. As with other white-collar crimes, though, the length of any potential prison sentence greatly depends on the severity of financial loss.

An attack that costs millions ramps up federal sentencing guidelines that a defendant faces, while one that is less costly often ends in probation, Nolan said.

Albert Gonzalez, an American who pleaded guilty in connection with the computer hacking of several major U.S. retailers, was sentenced to 20 years in prison last year. More than 40 million credit and debit card numbers were said to have been stolen in the scheme.

But last month, a former contractor for the animal rights group PETA Foundation was sentenced to a year of probation and $1,400 in restitution for logging into the organization's server from his Los Angeles apartment, according to court papers.

I was upset that I had been fired, the contractor, Vincent Tocce, said in his plea agreement. He admitted to deleting about 575 video and HTML files that he had previously worked on.

An attorney for Tocce could not be reached.

Federal prosecutors sometimes take tougher stances if it takes more resources to find a suspect, Nolan said.

The harder it is to find them, the more upset they get, but they don't really do a lot to them in terms of punishment, he said.

(Reporting by Dan Levine; Editing by Steve Orlofsky)

Cybercrime