Archive for April, 2013

A few weeks ago the anti-spam provider Spamhaus was hit by one of the biggest denial of service attacks ever seen, producing over 300 gbit in traffic. The technique used to generate most of the traffic was DNS Amplification, a technique which doesn’t require thousands of infected hosts, but exploits misconfigured DNS servers and a serious design flaw in DNS. We will discuss how this works, what it abuses and how Spamhaus was capable of mitigating the attack.

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An incredibly popular question, viewed 17000 times in its first 3 weeks, this question has even led to a new Sec.SE meta meme.

In fact, our top meta meme explains why – the First Rule of Crypto is “Don’t Roll Your Own!”

So, with that in mind, Polynomial’s answer, delivered with a liberal dose of snark, explains in simple language:

This home-brew method offers no real resistance against brute force attacks, and gives a false impression of “complicated” security…Stick to tried and tested key derivation algorithms like PBKDF2 or bcrypt, which have undergone years of in-depth analysis and scrutiny from a wide range of professional and hobbyist cryptographers.

Konerak lists out some advantages of going with an existing public protocol:

• Probably written by smarter people than you
• Tested by a lot more people (probably some of them smarter than you)
• Reviewed by a lot more people (probably some of them smarter than you), often has mathematical proof
• Improved by a lot more people (probably some of them smarter than you)
• At the moment just one of those thousands of people finds a flaw, a lot of people start fixing it

KeithS also gives more detail:

• MD5 is completely broken
• SHA-1 is considered vulnerable
• More hashes don’t necessarily mean better hashing
• Passwords are inherently low-entropy
• This scheme is not adding any significant proof of work

Along with further answers, the discussion on this post covered a wide range of issues – well worth reading the whole thing!

Liked this question of the week? Interested in reading it or adding an answer? See the question in full. Have questions of a security nature of your own? Security expert and want to help others? Come and join us at security.stackexchange.com.