Denial of Service Attacks

Sometimes when you try to access an Internet site but can’t, it’s more than an annoyance; sometimes you’re actually seeing an attack in progress. When hackers and criminals work to make specific Internet sites inaccessible, they’re carrying out a Denial of Service attack or DoS (sometimes called “DDoS” for “distributed” denial of service).

  • The Russian underground cybercrime community charges only $10 for an hour of distributed denial of service (DDOS) attack, which can potentially cost a target thousands of dollars.
  • An alternate way to cause denial of service is introduced in HTML5, where cybercriminals can flood a site server with thousands of page requests and cause it to crash.

A denial of service attack is different from a regular service outage because it’s been consciously and purposefully caused by a hacker or criminal. Hackers and criminals will levy denial of service attacks for three main reasons:

  • As part of a scheme to make money
  • To make a political statement
  • To cause mischief and mayhem

Denial of service attacks can make money as part of an extortion scheme. Criminals will approach website operators with an offer they think the operators can’t refuse: pay us money or we’ll shut down your website. In some cases, operators will pay the money to prevent or stop an attack. In these cases, it’s faster and cheaper for them to pay the bad guys and keep their site up than lose revenue while it’s down and they fight the attack.

In contrast to denial of service attacks to make money, some attacks are intended to make a political statement. The hacking group “Anonymous” is well-known for targeting and taking down sites associated with companies or governments whose activity or philosophy they object to. These attacks tend to be relatively short-lived; their goal is to get notoriety for their cause with the service outage.

Less common today, is the denial of service attack for no reason other than hackers simply wanting to prove to themselves and to others that they have the ability and resources to bring a site to its knees. The best example of this is the series of outages back in 2000 that took down CNN, eBay and Yahoo!.

If your computer is the victim of a successful virus or malware attack that turns it into a zombie and makes it part of a botnet, you could find yourself being part of a denial of service attack. The most common way that denial of service attacks are carried out is with botnets. Hackers and criminals use botnets that they own or rent and instruct the infected zombie computers to send network traffic to the target website. Since botnets can be made up of hundreds of thousands or even millions of zombie computers, they’re capable of inundating even the most robust and well-defended site with network traffic.

While denial of service attacks generally cause harm only to website operators, they can represent a significant danger for everyone on the Internet. Hackers and criminals have the ability to bring critical websites to a halt with these attacks. While not a directed denial of service attack, the Blaster and Sasser worms nearly crashed the Internet and show what large-scale concerted attacks could achieve.

Because denial of service attacks rely on botnets made up of infected zombie systems, keeping your computer or mobile device free of malware that can turn it into a zombie is critical for everyone’s protection. Running up-to-date antivirus and anti-malware software can help ensure that you’re not part of any denial of service attacks.

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