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Date: Wed, 27 Jan 2016 07:43:30 -0700
From: Kurt Seifried <>
To: oss-security <>
	secalert <>
Subject: Re: actively infiltrating IPv6 pools
 for scanning purposes

On Wed, Jan 27, 2016 at 4:24 AM, Luca BRUNO <> wrote:

> [cross-posted to pool-ntp and oss-sec]
> Hi,
> while reviewing network logs this morning I spotted some anomalies related
> to scan probes, pools and IPv6.
> It looks like Brad already observed and blogged about this some days ago,
> but I haven't seen this discussed in the usual ntp-pools, Debian and
> oss-sec ML, so I'm reposting this here:
> In summary, some machines (which seem related to the scanning
> project)
> are actively participating in as IPv6 endpoints.
> However, clients connecting to them for NTP timesync, are subsequently
> scanned
> by probes originating from * hosts.
> Confirming original report from Brad, I can add that those scanners seem to
> implement some kind of rate-limiting: they will timeout NTP and won't
> re-scan
> recent clients when doing multiple/subsequent NTP requests.
> Moreover, this is not targeted/restricted to the Debian pool only, but
> plague
> the whole IPv6 pool, as seen on a sample query to the RedHat pool:
> ```
> $ dig +short -t AAAA | grep -E
> ':[[:xdigit:]]00[[:xdigit:]]$'
> 2a03:b0c0:3:d0::18:b001
> $ dig +short -x 2a03:b0c0:3:d0::18:b001
> ```
> (Upon querying this server for NTP, the machine immediately got
> IPv6-scanned
> by
> services are the default NTP servers in many default
> configurations
> (at least most of Linux distro) and I guess that this kind of behavior is
> dangerously
> increasing the exposure level of way too many systems.
> For admins: can those rogue server be expunged from the pools,
> and the whole
> situation clarified? (Brad's post has a comprehensive endpoints
> list and
> helper tools for detection)
> For oss-sec crowd: is there anything we can do to improve the situation
> and avoid
> similar cases in the future? Should crowd-sourced and fundamental services
> like this
> be encouraged to move to a stronger WoT?
> Ciao, Luca
> --
>  .''`.  ** Debian GNU/Linux **  | Luca Bruno (kaeso)
> : :'  :   The Universal O.S.    | lucab (AT)
> `. `'`                          | GPG: 0xBB1A3A854F3BBEBF
>   `-  | Debian GNU/Linux Developer

Unfortunately there are strong economic incentives for this kind of
behavior. scanning is a great example, you want to scan the Internet of
things, this is easy with IPv4 (just bulk scan the used public space which
is like 3 billion IPs) and basically impossible with IPv6. Simply leverage
the fact that these IoT things often connect out to NTP servers by default
using the servers. No matter what you do on the pool
the people who want to scan will most likely be willing to spend time and
money to get at that data (hosting ntp servers, sniffing traffic to them,
etc.). Sadly what you need is business process to detect this activity (and
other forms of shenanigans) and then deal with the offender (e.g. remove
their ntp server from the pool).

Sadly we can't really rely on the IoT device makers to fix this, they have
basically 0 incentive to prevent scanners from hitting their products
(they're already sold, to late for the customer to make an informed

I'm also not sure that having scanners scan and publish these results is
such a bad thing, it raises awareness, and hopfully long term leads to
things like legislation that forces device makers to make safe devices
(e.g. no web interface with password "Admin").


Kurt Seifried -- Red Hat -- Product Security -- Cloud
PGP A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993
Red Hat Product Security contact:

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