(CNN) -- The attempt to bring down the heart of the Internet this week sounded ominous. But
experts say the attack was neither the most efficient nor likely way to inflict pain on the average Web surfer.
people had no idea this was happening," said Hari Balakrishnan, a computer science professor at the Massachusetts Institute
of Technology. "If the top five most-visited sites were down, that's when people will tell you their service was disrupted."
It's called a "denial of service" attack. And investigators are hard at work trying to find those responsible for
the assault, said FBI agent Steven Berry.
What happened this week is nothing new, Balakrishnan said. "I'm sure the
top 20 portals in the world are seeing attacks as we speak."
Hackers are constantly trying to disrupt the servers
where companies, schools and governments maintain their Web sites by overloading them with useless information.
Security specialists -- working for the government and companies -- monitor systems round-the-clock to ensure that
hackers can be stopped in time. But on occasion, the attacks have been so fierce they've brought down sites such as eBay,
Amazon and Yahoo.
Servers match requests with sites
The 13 servers hit this week -- key to the Internet's naming
system -- are responsible for matching Internet addresses with users' requests.
The attack, which began around 4:45
p.m. EDT Monday, flooded the 13 domain-name service root servers around the world with 30 to 40 times the normal amount of
data. Seven of the servers were affected enough to have periods of "zero-reachability," according to Web security firm Matrix
It took about an hour for security specialists to enact defensive measures and restore service.
The attack failed to disrupt service because the data on the 13 key servers is replicated tens of thousands of times
by Internet service providers and other computers around the world.
Only a small fraction of such requests -- as low
as 6 percent by some estimates -- ever hit the 13 systems. Many of them are for domains that don't exist, misconfigured
queries or seldom-visited sites, Balakrishnan said.
In some ways, the attacks demonstrate how the government and
companies stand ready to thwart hackers, experts say. But it also highlights the need to stay ahead of those that may attempt
to bring down popular sites or steal credit card or other sensitive data.
"This is always an arms race," said Richard
DeMillo, director of the Information Security Center at the Georgia Institute of Technology. "We shore up the defenses of the
Internet and the attackers shore up their tools."