Level(3) DNS Spoofing All Domains

Tue Nov 19 15:41:42 UTC 2019

Are you a CL/L3 customer? Those resolvers have only ever been for “customers” even though they would resolve for anyone. They started injecting NXDOMAIN redirects a while ago for non-customers.

From: NANOG <nanog-bounces at nanog.org> On Behalf Of Marshall, Quincy
Sent: Monday, November 18, 2019 12:45 PM
Subject: Level(3) DNS Spoofing All Domains

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This is mostly informational and may have already hit this group. My google-foo failed me if so.

I discovered that the CenturyLink/Level(3) public DNS (4.2.2.2, etc) are spoofing all domains. If the hostname begins with a “w” and does not exist in the authoritative zone these hosts will return two Akamai hosts.

[root at localhost ~]# dig +short w3.dummydomaindoesntexist.gov @4.2.2.2
23.202.231.167
23.217.138.108
[root at localhost ~]# dig +short w3.dummydomaindoesntexist.net @4.2.2.2
23.202.231.167
23.217.138.108
[root at localhost ~]# dig +short w3.dummydomaindoesntexist.com @4.2.2.2
23.202.231.167
23.217.138.108
[root at localhost ~]# dig +short w3.dummydomaindoesntexist.org @4.2.2.2
23.202.231.167
23.217.138.108

My apologies if this is old news.

Lawrence Q. Marshall

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