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What is a Denial of Service Attack? How Can I Avoid It?

July 29, 2010

A denial of service occurs when a user is forbidden from accessing a website or email because that entity has exceeded the limitations of its host.  A denial of service attack attempts to utilize all the bandwidth or data space alotted to a website so that others can no longer access it.  A distributed denial of service attack (DDoS) occurs when a hacker utilizes mutliple computers to accomplish the denial of service.  Often, hackers will take over computers without the computer owner’s knowledge or consent.

When you type in a web address, the browser sends a request to that websites host.  The host has alotted a certain number of requests the website can acheive.  An attacker simply automates a series of requests so that the system is overrun and legitimate users can no longer access the site’s content.

Similarly, the same can be achieved with email.  Most people know that email services have certain capacity limitations.  You can only save so many emails and attachments before your provider cuts you off.  An attacker can flood the inbox with emails and attachments so that the space is filled quickly, and service is suspended.

A DoS can also involve overuse of a computers processing capabilities through the execution of malware.

For example,‘s /b/ message board posters used a denial of service attack to retaliate against online magazine Gawker.  Gawker caught the attention of /b/ after the magazine reported on /b/’s harassment {link} of 11-year-old video-blogger Jessi Slaughter.  The attack rendered the Gawker site temporarily unavailable.

From a server standpoint, prevention of a DoS attack is difficult, and should be left to IT professionals who can use firewalls, intrusion prevention systems, cleaning proxies, and blackholing to attempt to keep attackers at bay.  DoS attacks are illegal under the National Information Infrastructure Protection Act of 1996.

Keeping your computer from being part of a DDoS is not entirely possible.  Firewalls, anti-virus and generally safe browsing and downloading habits are the best preventative medicine.  Don’t worry about legal ramifications, though.  NIIPA requires violators intentionally engage in an attack.

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