Archive for February 15th, 2009

Feb 15, '09

I’ve just submitted a (rather critical) public response to an ICANN working group report on fast-flux hosting (read the whole thing here).

Many phishing websites (and other types of wickedness) are hosted on botnets, with the hostname resolving to different machines every few minutes or hours (hence the “fast” in fast-flux). This means that in order to remove the phishing website you either have to shut-down the botnet — which could take months — or you must get the domain name suspended.

ICANN’s report goes into lots of detail about how fast-flux hosting has been operated up to now, and sets out all sorts of characteristics that it currently displays (but of course the criminals could do something different tomorrow). It then makes some rather ill-considered suggestions about how to tackle some of these symptoms — without really understanding how that behaviour might be being used by legimitate companies and individuals.

In all this concentration on the mechanics they’ve lost sight of the key issue, which is that the domain name must be removed — and this is an area where ICANN (who look after domain names) might have something to contribute. However, their report doesn’t even tackle the different roles that registries (eg Nominet who look after the .UK infrastructure) and registrars (eg Gradwell who sell .UK domain names) might have.

From my conclusion:

The bottom line on fast-flux today is that it is almost entirely associated with a handful of particular botnets, and a small number of criminal gangs. Law enforcement action to tackle these would avoid a further need for ICANN consideration, and it would be perfectly rational to treat the whole topic as of minor importance compared with other threats to the Internet.

If ICANN are determined to deal with this issue, then they should leave the technical issues almost entirely alone. There is little evidence that the working group has the competence for considering these. Attention should be paid instead to the process issues involved, and the minimal standards of behaviour to be expected of registries, registrars, and those investigators who are seeking to have domain names suspended.

I strongly recommend adopting my overall approach of an abstract definition of the problem: The specific distinguisher of a fast-flux attack is that the dynamic nature of the DNS is exploited so that if a website is to be suppressed then it is essential to prevent the hostname resolving, rather than attempting to stop the website being hosted. The working group should consider the policy and practice issues that flow from considering how to prevent domain name resolution; rather than worrying about the detail of current attacks.


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