The incident follows a high profile hacking of the National Research Council last year an episode the federal government blamed on a Chinese state sponsored player. Beijing has denied involvement, accusing Canada of making irresponsible accusations.

Denial of service attacks, which bombard a site with traffic, are a common means of shutting down a web server.

Are these problems always deliberate attacks? No, there can be accidental denial of service events in which a web site has a sudden spike in popularity which produces more hits than it can handle.

OTTAWA No personal information was compromised during a cyberattack that temporarily crippled some federal government websites, says Public Safety Minister Steven Blaney.

"We are living in a democracy," Blaney said. "And there are many ways to express your views."

However, Blaney said there were no excuses for such an attack, noting "law enforcement agencies" were looking into the matter.

The government stresses it has since invested energy and millions of dollars in a national cybersecurity strategy.

What is a denial of service attack? Most commonly, these events occur when mischief makers or hackers simply flood a target computer with more traffic than it was built to handle. This can involve sending more connection requests than a server can handle, or sending enormous amounts of random data to use up the target's bandwidth. They all essentially leave the victimized computer in the position of someone trying to sip from a fire hose.

OTTAWA Some of the federal government's computers and websites went down Wednesday under what is called a denial of service attack.

Anonymous has carried out cyberattacks against governments, corporations and others in the name of free speech, Internet liberties and anti capitalist causes.

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"We are working on restoring services as soon as possible," said a brief, late afternoon statement from Dave Adamson, the government's acting chief information officer.

The Anonymous online collective claimed responsibility for the attack which shut down several federal sites and played havoc with email as a protest against the recent passage of the federal anti terrorism bill.

"Cybersecurity is an issue that we take very seriously," Blaney said.

There was no immediate confirmation that the loosely knit coalition was actually behind the assault on federal sites.

"We continue to be vigilant in Women Canada Goose Liuigno Parka Coat Grey New Zealand monitoring any potential vulnerabilities."

Do these attacks steal data? Normally, the goal is simply to shut down the target, paralyzing an email system, for example. But they can cause serious damage to systems.

Assaults that crippled computer systems at the Finance Department and Treasury Board in 2010 were linked to efforts possibly originating in China to gather data on the potential takeover of a Canadian potash company.

Where does the traffic come from? Some attacks link a number of systems together to pour traffic into the target computer until it can't handle that data and do its regular work, too. In a distributed denial of service attack, the hacker uses a security flaw to seize control of other computers and use them to send vast amounts of data to a website or send spam to targeted email address. This is a distributed attack because the attacker is using many computers to create a denial of service.

´╗┐Anonymous collective claims responsibility for attack on federal websites