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Scientific American Instant Egghead
It happens all the time.
You're trying to make a last-minute purchase,
or pay a bill online,
but you can't get the website to load.
A technical glitch, or maybe something more nefarious.
The website could be under attack.
One of the most common ways to bring down a website
is to flood the servers running it with so much traffic
they simply can't handle the volume.
This is called a Denial of Service attack,
and it can slow a website's performance to a crawl,
or force its owner to take the site down completely until the attack is over.
To use an analogy, think of a website as an airport,
and the requests to communicate as aircraft wanting to land there.
When traffic increases, an airport can make additional runway space available.
Likewise, a server can offer additional connections into the website.
With a DoS attack, too many planes want to land at the same time,
and many of those planes are actually drones
set up by the attacker just to snarl traffic.
That means air traffic controllers have to close down the airport and divert traffic.
Access is denied not only to the drones, but to legitimate travelers as well.
But it's not quite that simple.
There are several different kinds of DoS attack.
When traffic comes from many different sources, it's called a distributed DoS attack.
Many of these sources are computers or other devices connected to the Internet
that have been infected with malware and turned into zombie-like bots.
An attacker can direct thousands, or even tens of thousands of these devices to create a botnet.
In another type of attack, two sites are hit at once.
An attacker will flood Website 1 with requests that have a faked IP address.
When it can't handle anymore requests, it generates error messages.
Instead of sending those responses back to the attacker's computer,
it sends them to the faked IP address, which is actually Website #2.
One site under duress has unwittingly redirected the attack to another site,
and the attacker didn't have to do any extra work.
It's hard to prevent DoS attacks, but websites can lessen the impact
by backing up their data to multiple locations.
This way, if its servers come under attack,
it can continue to operate from a different location,
and we can get on with our lives.
For Scientific American's Instant Egghead, I'm Larry Greenemeier.