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Around the peak of the dot-com era there was a series of incidents that introduced most users to the term DDoS, or distributed-denial-of-service attack. These came to be known as the “Mafiaboy” attacks. The attacks were somewhat scary in that they brought down, one by one, the biggest and most prominent Web sites on the Internet. Every day we wondered who was next, and—gasp!—could it be us? Eventually, the site for which I wrote the most was taken down just like all the big guys.
The attacker turned out to be a (lets be generous) troubled Canadian teenager who had managed to crack groups of computers and command them in a coordinated attack against a particular site. If you could get past the basic immorality of the act, the guy did show some talent.
The most recent famous DDoS attacks have been from worms, such as MyDoom, that attack essentially political targets such as microsoft.com. Even more recently, Panda Software described the Cone.E worm, which launches an attack against www.irna.com—which is the site of the Islamic Republic News Agency, aka the official news agency of Iran.
But DoS attacks arent just for the big guys. People in the trenches say they happen all the time for all kinds of reasons. I spoke with Paul Froutan, VP of engineering of Rackspace Managed Hosting, about some of the ways they happen and techniques that can be used to stop or prevent them.
Next page: Ask not why the DDoS bell tolls for thee.
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You might ask why you, who monopolized your industry or sued customers for using someone elses product, should be the target of a DDoS attack? You might as well ask why theres random street crime. The answer is that the Internet is a rough neighborhood, and even little guys have disgruntled former employees and customers who feel cheated, not to mention ex-spouses and competitors. Trust me, it really could happen.
Most Web sites dont have or need the resources that Microsoft or even The SCO Group put in theirs for normal business, and it doesnt take an army of zombied clients to bring them down. Just a few clients, focused on the job, can cause problems for a Web site. Froutan says that at his company theyve seen such attacks go on for days at a time. Experience with the MyDoom worms certainly bears that out.
At the Web-site end, you can get appliances such as devices from Webscreen that purport to stop such attacks. Theyre basically specialized firewalls, and theyre expensive (here I found a quote for a low-end box for $7,999). And even if they prevent the attack from reaching or disabling your Web server, the attack can still consume all your Internet bandwidth.
No matter who your provider is, you need to know whom you can call when something goes wrong on your site. A really good provider will be monitoring traffic to customer sites and will know that there is a problem before you do, but if youre technical enough you should try to keep a sense of what kind of traffic is hitting your site. Your providers facilities should be able to tell you that.
Unlike the Mafiaboy attacks, which were orchestrated on zombied university systems, most DDoS attacks come from consumer systems. MyDoom.A was preprogrammed to DDoS-specific sites, but lots of worms have backdoors that attackers can use to take control and launch whatever attacks they want. Im sure some attacks are actually malfunctioning programs, unintentionally whacking on a particular server.
Next page: What to do in the face of a DDoS attack.
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So what can you do? The primary effect of most attacks is to consume all your Internet bandwidth, so you would do well to have your hosting at a very large managed host with gobs of bandwidth and the appliances to mitigate the effects of the attack. This, of course, is the advertising portion of this column for Rackspace, but they do have a good point. A big company like that is in a better position to protect you than a small one, no matter how smart and nimble the small ones are. Heres an announcement from last year where they announced an anti-DDoS initiative.
You can also try to shut down the attacking systems. Your logs will show the address of the attacker (its conceivable that its spoofed, but probably not). Its a short step from there to determining the ISP and contacting its abuse people. Unfortunately, these ISPs arent always quick to contact or shut down the systems of paying customers who just happen to be attacking someone elses systems.
A lot of these attacks subside over time, either when the ISP eventually stops them or when the customer reboots their system, for example. Or you can resort to stopping specific addresses. An attacker from an actual business domain will likely be stopped quickly.
DoS attacks have a kind of second-class status in the security world because they arent as scary or destructive as a lot of other attacks out there. Theres something to this, but its still a shame, since they can shut a business down every bit as much as a more destructive attack. One day the Internet may change to make them harder, but for now you have to be aware of them and ready to react.
Security Center Editor Larry Seltzer has worked in and written about the computer industry since 1983.
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