What are DoS and DDoS attacks?

What are DoS and DDoS attacks?

If your favourite website is down, there’s a chance it’s
suffering a Denial of Service (DoS) attack. This is more
likely if the site is an online shop, a bookie or another
site that relies financially on being online at all times.
Enemy at the gates
A DoS attack tries to make a web resource unavailable to
its users by flooding the target URL with more requests
than the server can handle. That means that during the
attack period, regular traffic on the website will be either
slowed down or completely interrupted.
A Distributed Denial of Service (DDoS) attack is a DoS
attack that comes from more than one source at the
same time. A DDoS attack is typically generated using
thousands (potentially hundreds of thousands) of
unsuspecting zombie machines. The machines used in
such attacks are collectively known as “botnets” and will
have previously been infected with malicious software, so
they can be remotely controlled by the attacker.
According to research, tens of millions of computers are
likely to be infected with botnet programs worldwide.
Cybercriminals use DoS attacks to extort money from
companies that rely on their websites being accessible.
But there have also been examples of legitimate
businesses having paid underground elements of the
Internet to help them cripple rival websites. In addition,
cybercriminals combine DoS attacks and phishing to
target online bank customers. They use a DoS attack to
take down the bank's website and then send out phishing
e-mails to direct customers to a fake emergency site
instead.
DoS attacks have proven to be very profitable and are
taking over the Internet. The Network Infrastructure
Security Report points out that DDoS attacks have
increased by 1000 per cent since 2005. 2010's biggest
attack doubled in scale compared to 2009, with one
attack in particular bombarding its target at 100 gigabits
per second.
A new type of warfare
A WikiLeaks story from 2010 has redefined DDoS attacks
as a legitimate form of protest. Computing expert Richard
Stallman has gone on record saying DDoS attacks are
"the Internet equivalent of a mass demonstration."
Stallman defines such "demonstrations" as being
separate from hacking or cracking, and compares them
with harmless demonstrations that temporarily closed
down several British stores recently, in order to highlight
corporate tax evasion.
However, you should know that DDoS attacks are illegal
under the Computer Fraud and Abuse Act and can lead to
prison time.
Furthermore, new factors that arise every day are making
DDoS attacks a big concern, especially with the growth
of high-speed fibre optic Internet connections and mobile
computing devices.