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.