BCP 38 addendum (was: New Active Exploit: memcached on port 11211 UDP & TCP being exploited for reflection attacks)

Mike Hammett nanog at ics-il.net
Fri Mar 2 20:18:33 UTC 2018


https://en.wikipedia.org/wiki/Reverse_path_forwarding#Loose_mode towards transit. 

https://en.wikipedia.org/wiki/Reverse_path_forwarding#Strict_mode towards customers. 

Peers... *shrugs*. 



----- 
Mike Hammett 
Intelligent Computing Solutions 

Midwest Internet Exchange 

The Brothers WISP 

----- Original Message -----

From: "Todd Crane" <todd at toddcrane.com> 
To: "NANOG list" <nanog at nanog.org> 
Cc: "Job Snijders" <job at ntt.net> 
Sent: Thursday, March 1, 2018 12:57:53 PM 
Subject: BCP 38 addendum (was: New Active Exploit: memcached on port 11211 UDP & TCP being exploited for reflection attacks) 

Question: 
Since we cannot count on everyone to follow BCP 38 or investigate their [email protected], I was thinking about the feasibility of using filtering to prevent spoofing from peers’ networks. 

With the exception of a few edge cases, would it be possible to filter inbound traffic allowing only packets with source addresses matching the peer’s BGP announcement? Theoretically it should be a two way street to any address I can receive from, thus if I can’t send to it, I shouldn't be receiving from it. I realize this is not currently a feature of any router (to my knowledge), but could it be implemented into some NOSs fairly easily and jerry-rigged into others for the time being. 

This would allow us to peer with OVH et al, and not worry as much. Furthermore, whereas BCP 38 is reliant upon everybody, this could significantly reduce amplification attacks with even just a handful of adopters. 


—Todd 

> On Feb 28, 2018, at 6:52 PM, Job Snijders <job at ntt.net> wrote: 
> 
> On Tue, Feb 27, 2018 at 09:52:54PM +0000, Chip Marshall wrote: 
>> On 2018-02-27, Ca By <cb.list6 at gmail.com> sent: 
>>> Please do take a look at the cloudflare blog specifically as they 
>>> name and shame OVH and Digital Ocean for being the primary sources 
>>> of mega crap traffic 
>>> 
>>> https://blog.cloudflare.com/memcrashed-major-amplification-attacks-from-port-11211/ 
>>> 
>>> Also, policer all UDP all the time... UDP is unsafe at any speed. 
>> 
>> Hi, DigitalOcean here. We've taken steps to mitigate this attack on 
>> our network. 
> 
> NTT too has deployed rate limiters on all external facing interfaces on 
> the GIN backbone - for UDP/11211 traffic - to dampen the negative impact 
> of open memcached instances on peers and customers. 
> 
> The toxic combination of 'one spoofed packet can yield multiple reponse 
> packets' and 'one small packet can yield a very big response' makes the 
> memcached UDP protocol a fine example of double trouble with potential 
> for severe operational impact. 
> 
> Kind regards, 
> 
> Job 





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