[routing-wg] Detecting, mitigating, and preventing distributed large-scale prefix de-aggregation attacks

Hi Nick,

As we wrote in the mail and the write-up (§7): mitigation is quick and 
fairly easy (to the point where damage is limited to the human response 
time/time-to-action).

Our notification aimed at (i) cutting down the the time-to-action by 
re-raising awareness for the problem and (ii) providing operators 
(especially of smaller networks) with prevention mechanisms to lower the 
impact on their networks until transit providers and IXPs acted.

Best regards,

Lars

On 20.10.22 23:15, Nick Hilliard wrote:
> Lars Prehn wrote on 20/10/2022 20:23:
>> If you want to know more about the research that initiated this 
>> notification (including our concluded private disclosure process), 
>> you may find a write-up at:
>>
>> https://arxiv.org/pdf/2210.10676.pdf
>
> Lars,
>
> thanks for sending your findings to routing-wg. The impact of 
> deaggregation of ipv6 prefixes on router resources has been understood 
> since well before ipv6 was standardised.
>
> Your paper describes an attack which can either use a provider's 
> customer cone or else use a selection of different transit providers 
> to inject smaller numbers of prefixes from different injection points 
> into either a providers routing table, or the ipv6 dfz.  Your argument 
> is roughly equivalent to stating that if you send 20,000 cars from 
> different starting points to a single destination, that you will end 
> up with gridlock, as the taxi industry in Moscow discovered a couple 
> of weeks ago - this isn't news for either cars or routing table 
> prefixes. There are many other easily-staged attacks which are also 
> efficient at causing disruption, e.g. sending 1tbit/s of data at a 
> destination, gluing oneself to the road on a commuter trunk during 
> rush hour, cutting fibre cables in chambers, etc. All of these are low 
> cost, regularly tested, and are known to work well.
>
> Your list of takeaways in section 6.1 is correct, but it stopped at 
> the point of detection and mitigation.  Routing tables are monitored, 
> and some people / organisations have alerts triggered, particularly 
> transit providers.  Another is that routing operations people tend to 
> notice things like routers and routing tables blowing up. In other 
> words, you will cause damage if you try this in anger, but fairly 
> quickly the source(s) will be noticed and you'll find that mitigation 
> action will be taken. As quickly as providers might increase prefix 
> limits on a bgp session, they will drop them too, or shut down the 
> session entirely, or terminate your free ipv6 transit, or cut off your 
> ixp peering.
>
> This is important because one of the more important aspects of network 
> reliability is not closing off all angles of potential attack / 
> failure, but ensuring that detection and time-to-recovery are optimised.
>
> The Vultr incident on October 5 this year was noticed fairly quickly 
> on operator forums, both because of alerting on router FIB resource 
> usage and control plane CPU usage.  Incidentally, production 
> de-peering happened as a result of the incident, although hopefully 
> that has been undone at this point.
>
> Nick