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Re: Spoofing ASNs (Re: SNMP DDoS: the vulnerability you might not know you have)
From: Jared Mauch <jared () puck nether net>
Date: Thu, 8 Aug 2013 13:45:03 -0400

On Aug 8, 2013, at 1:40 PM, Matthew Petach <mpetach () netflight com> wrote:

On Thu, Aug 8, 2013 at 10:29 AM, Jared Mauch <jared () puck nether net> wrote:

On Aug 1, 2013, at 2:31 AM, Saku Ytti <saku () ytti fi> wrote:

On (2013-07-31 17:07 -0700), bottiger wrote:

But realistically those 2 problems are not going to be solved any time
in the next decade. I have tested 7 large hosting networks only one of
them had BCP38.

I wonder if it's truly that unrealistic. If we target access networks, it
seems impractical target.

We have about 40k origin only ASNs and about 7k ASNs which offer transit,
who could arguably trivially ACL those 40k peers.

If we truly tried, as a community to make deploying these ACLs easy and
actively reach out those 7k ASNs and offer help, would it be unrealistic to
have ACL deployed to sufficiently large portion of networks to make
spoofing impractical/expensive?

The following is a sorted list from worst to best of networks that allow spoofing: (cutoff here is 25k)

(full list - http://openresolverproject.org/full-spoofer-asn-list-201307.txt )

Count   ASN#
1323950 3462
1300938 4134
1270046 8151
1213972 9737

For the technically clueless among us...

what does "count" refer to in this output?
How many times you were able to spoof
an address through them?  How many
different addresses you could spoof through
them?  How many spoofed packets made it
through before being blocked?

It's kinda hard to know what the list
represents without a bit of explanation
around it.  ^_^;

Number of unique IPs that spoofed a packet to me. (eg: I sent a packet to and responded).

If those ASNs are downstream to you, or you are part of that ASN, you can ask for a list of the IPs involved.

Either way, if you have 1.2 million hosts, it may be a lot of BCP38 you need to apply.

- Jared

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