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How to detect and thwart DDoS attacks

Has progress been made in fighting DDoS attacks?

As the distributed denial-of-service attacks spawned by this week's WikiLeaks events continue, network operators are discussing what progress, if any, has been made over the past decade to detect and thwart DoS attacks.

Participants in the North American Network Operators Group (NANOG) e-mail reflector are debating whether any headway has been made heading off DDoS attacks in 10 years. The discussion is occurring while WikiLeaks deals with DDoS attacks after leaking sensitive government information, and sympathizers launch attacks against Mastercard, Visa, PayPal and other significant e-commerce sites.

"February 2000 weren't the first DDoS attacks, but the attacks on multiple well-known sites did raise DDoS' visibility," writes Sean Donelan, program manager of network and infrastructure security at the Department of Homeland Security, on the NANOG reflector. "What progress has been made during the last decade at stopping DDoS attacks?"

From there, multiple participants debate whether progress has indeed been made and if DDoS attack sources and targets can do anything proactively and effectively to detect, prevent and/or mitigate an attack.

"If anything, the potential is worse now than it ever has been unless you have just ridiculous amounts of bandwidth, as the ratios between leaf user connectivity and data center drops have continued to close," participant Blake Dunlap responds. "The finger of packety death may be rare, but it is more powerful than ever, just ask Wikileaks; I believe that they were subject to 10Gbit+ at times. At least the frequency has dropped in recent years, if not the amplitude, and I am thankful for that."

WikiLeaks had its domain name service terminated last week after repeated DDoS attacks against the WikiLeaks site.

Another participant, Arturo Servin, responds, "One big problem of DDoS is that sources (the host of botnets) may be completely unaware that they are part of a DDoS. (On) the other hand the target of a DDoS cannot do anything to stop an attack besides adding more (bandwidth) or contacting one by one the whole path of providers to try to minimize the effect."

On the glass-half-full side, some participants say using a distributed architecture with anycast and loads of bandwidth will help mitigate attacks, or limit them to a subset of nodes. Others say eliminating botnets is a preventative measure.

"DDoS is just a symptom. The problem is botnets," states Roland Dobbins, solutions architect at Arbor Networks. "Preventing hosts from becoming bots in the first place and taking down existing botnets is the only way to actually prevent DDoS attacks. Note that prevention is distinct from defending oneself against DDoS attacks."

Easier said than done.

"Actually, botnets are an artifact," responds participant Bill Manning. "Claiming that the tool is the problem might be a bit shortsighted. With the evolution of Internet technologies I suspect botnet-like structures to become much more prevalent and useful for things other than coordinated attacks."

But while ways to mitigate and perhaps prevent attacks have emerged over the decade, so too have new attack vectors. As new methods to thwart attacks are discovered, attackers discover new way to attack.

"Nowadays the consumers have a lot more bandwidth and it's easier than ever to set up your own botnet by infecting users with malware and alike," writes Jonas Frey of Probe Networks.

"I do not see a real solution to this problem right now," Frey writes. "There's not much you can do about the unwillingness of users to keep their software/OS up to date and deploy anti-virus/anti-malware software (and keep it up to date). Some approaches have been made, like cutting off Internet access for users which have been identified by ISPs for being a member of some botnet being infected. This might be the only long-term solution to this probably. There is just no patch for human stupidity."

Arbor's Dobbins begs to differ:

"The tolls and the techniques, the technologies and best practices - this information is out there, it's available. Folks need to learn about this stuff because, if they do the searches and do some reading they can empower themselves to defend themselves and their networks, and their customers, from DDoS attack. It isn't rocket science; it does require some skill set, some dedication and some hard work, but it can be done. And it's done successfully by organizations around the world everyday. These are the organizations you don't tend to read about in the press."

Dobbins believes this week's attacks on the Mastercard, Visa and PayPal sites, combined with last week's attacks on the WikiLeaks site, have heightened awareness among IT officials to the need to proactively prepare for a DDoS eventuality.

"These attacks are not very sophisticated or high-bandwidth," he says. "But they've been able to achieve disproportionate impact due to the unpreparedness of the defenders."

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