What is a denial-of-service (DoS) attack?

What is a denial-of-service (DoS) attack?

September 7, 2007

In  a  denial-of-service (DoS) attack, an attacker attempts to prevent legitimate  users from accessing information or services. The most common and obvious type of DoS attack occurs when an attacker “floods”  a  network  with  information.  When  you  type  a URL for a particular  web  site  into your browser, you are sending a request to that  site’s  computer  server  to  view the page. The server can only process  a  certain  number  of  requests  at  once, so if an attacker overloads  the  server  with  requests, it can’t process your request. This is a “denial of service” because you can’t access that site.

An attacker can use spam email messages to launch a similar attack on your email account. By sending many, or  large, email messages to the account, an attacker can consume your quota, preventing you from receiving legitimate messages.

What is a distributed denial-of-service (DDoS) attack?

In  a distributed denial-of-service (DDoS) attack, an attacker may use
your  computer  to  attack  another  computer.  By taking advantage of
security vulnerabilities or weaknesses, an attacker could take control
of  your  computer.  He  or she could then force your computer to send
huge  amounts  of  data to a web site or send spam to particular email
addresses.  The  attack is “distributed” because the attacker is using
multiple  computers,  including yours, to launch the denial-of-service

How do you avoid being part of the problem?

nfortunately, there are no effective ways to prevent being the victim of a  DoS or DDoS attack, but there are steps you can take to reduce the likelihood that an attacker will use your computer to attack other computers:
* Install   and  maintain  anti-virus  software
* Install  a  firewall and configure it to restrict traffic
* Follow good security practices for distributing your email address

Not  all  disruptions to service are the result of a denial-of-service
attack.  There may be technical problems with a particular network, or
system  administrators  may  be  performing  maintenance. However, the
following symptoms could indicate a DoS or DDoS attack:
* unusually slow network performance (opening files or accessing web
* unavailability of a particular web site
* inability to access any web site
* dramatic  increase  in  the  amount  of  spam  you receive in your

Even if you do correctly identify a DoS or DDoS attack, it is unlikely that  you will be able to determine the actual target or source of the attack.  Contact   the   appropriate   technical   professionals  for  assistance.