Security Corner

Mar 30 2013   3:01PM GMT

Spamhaus target of massive DDoS attack

Ken Harthun Ken Harthun Profile: Ken Harthun


If you have noticed a bit of sluggishness on your internet connection in the past week or so, it could be due to the most massive DDoS attack ever recorded. Here’s what’s happening according to Naked Security:

A little over a week ago a questionable internet hosting provider in The Netherlands called Cyberbunker took umbrage with SpamHaus, an non-profit organization that was founded in 1998 to take on spammers and the internet hosts who profit from their activities.

How big is the attack? At times it has been reported to be as large as 300 gigabits per second. Traditionally even large botnets are only able to deliver hundreds of megabits or a few gigabits per second.

Ouch! That’s huge. It seems that many primary internet backbones (“tier 1 service providers”) are being overwhelmed by the volume of traffic. That’s why you may have noticed the slowdown on the internet. I certainly did, but since it was most prevalent where I work, I didn’t think much of it. Our bandwidth is always strained when school is in session. I did find it a bit odd that my home connection seemed sluggish. It all became clear with the report of the DDoS attack.

So, if large botnets aren’t capable of delivering such a volume of traffic, what is causing it? It’s a large scale DNS amplification/reflection attack taking advantage of misconfigured DNS servers that will allow anyone to query them without any filtering or rate-throttling. It’s a huge problem as there are reportedly more than 21.7 million such servers online (Open Resolver Project). A Microsoft TechNet article provides a high-level summary of this type of attack:

A DNS amplification attack (aka DNS reflection attack) is a type of distributed denial of service (DDos) attack that takes advantage of the fact that a small DNS query can generate a much larger response. When combined with source address spoofing, an attacker can direct a large volume of network traffic to a target system by initiating relatively small DNS queries.

I’ll leave it at that for now. I plan to give a more detailed analysis in a future post.

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