North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: New Internet-draft on DDOS defense...

  • From: Vipul Shah
  • Date: Fri May 12 02:56:49 2000

>I have some concerns with this draft. The proposed change does lower the
>risk of damages if one system on a shared-media LAN is compromised, but
>only for this one type of attack. It seems to me it'd be possible to
>generate other types of packets which are broadcast/multicast which
>could elicit an ICMP response, and such attacks are not something which
>can be cured without breaking a lot of functionality. While ICMP ECHO
>packets are a preferred mechanism today, they're far from the only types
>of packets which are problematic.
>Where RFC2644 prevents ALL types of directed broadcast traffic, this
>draft will only have a useful impact on ICMP ECHO, and only in a limited
>case. I have to question whether there's sufficient benefit here to
>warrant opening up the IP stacks on end stations.

Will you please list down the other types of  packets (apart from ICMP
ECHO packets) used to generate broadcast response and can lead to
 an attack. We can extend our solution further to include other types of 
packets, if possible.

>An alternative to the suggested approach is the use of packet filters on
>end stations. For example, with Linux systems (and probably others)
>ipchains can be used to filter the types of traffic a host will respond
>to, regardless of what a border router or firewall ahead of it allows. I
>generally advocate the use of such facilities where possible as it adds
>an extra line of defense.
>Rate limiting of certain types of traffic (e.g. ICMP) is also a way to
>address the type of problem this draft is concerned with, and again is
>capable of addressing all ICMP, rather than just ICMP ECHO/ECHO REPLY.

Rate limiting and filtering may reduce the impact of Smurf attack, but the attack
 itself is not prevented!


>Overall impression of the draft: not a terrible idea, but unclear if
>it's sufficiently beneficial to warrant the effort to implement.
>Daniel Senie                                        [email protected] 
>Amaranth Networks Inc.