Application or Software to detect or Block unmanaged swicthes
owen at delong.com
Fri Jun 8 18:20:47 UTC 2018
There are a few options.
1. Most likely it will leak information (STUN, NAT-PMP, etc.).
2. You could look obvious signs of NATted traffic. (e.g. re-use of the same
source port number to different destinations from the box, etc.)
3. You can look at the TTL or Hop-Count on packets coming out of the box.
Most NAT routers (I believe DD-WRT included, IIRC) do still decrement
the TTL/Hop-Count (v4/v6) when passing the packet.
4. NMAP the device… DD-WRT will usually look strikingly different from most
I’m sure there are other ways, but those are the first 4 that spring to mind. Each
could be defeated by a particularly careful/clever implementer, but in an enterprise,
usually it makes little sense to go to that much trouble to violate policy. Universities
are an exception as that’s a whole different set of equations on risk/benefit.
> On Jun 8, 2018, at 10:32 , David Hubbard <dhubbard at dino.hostasaurus.com> wrote:
> This thread has piqued my curiosity on whether there'd be a way to detect a rogue access point, or proxy server with an inside and outside interface? Let's just say 802.1x is in place too to make it more interesting. For example, could employee X, who doesn't want their department to be back billed for more switch ports, go and get some reasonable wifi router, throw DD-WRT on it, and set up 802.1x client auth to the physical network using their credentials? They then let their staff wifi into it and the traffic is NAT'd. I'm sure anyone in a university setting has encountered this. Obviously policy can forbid, but any way to detect it other than seeing traffic patterns on a port not match historical once the other users have been combined onto it, or those other users' ports go down?
> On 6/7/18, 10:18 AM, "NANOG on behalf of Mel Beckman" <nanog-bounces at nanog.org on behalf of mel at beckman.org> wrote:
> When we do NIST-CSF audits, we run an SNMP NMS called Intermapper, which has a Layer-2 collection feature that identifies the number and MACs of devices on any given switch port. We export this list and cull out all the known managed switch links. Anything remaining that has more than one MAC per port is a potential violation that we can readily inspect. It’s not perfect, because an unmanaged switch might only have one device connected, in which case it wont be detected. You can also get false positives from hosts running virtualization, if the v-kernel generates synthetic MAC addresses. But it’s amazing how many times we find unmanaged switches squirreled away under desks or in ceilings.
>> On Jun 7, 2018, at 4:54 AM, Jason Hellenthal <jhellenthal at dataix.net> wrote:
>> As someone already stated the obvious answers, the slightly more difficult route to be getting a count of allowed devices and MAC addresses, then moving forward with something like ansible to poll the count of MAC’s on any given port ... of number higher than what’s allowed, suspend the port and send a notification to the appropriate parties.
>> All in all though sounds like a really brash thing to do to your network team and will generally know and have a very good reason for doing so... but not all situations are created equally so good luck.
>> The fact that there's a highway to Hell but only a stairway to Heaven says a lot about anticipated traffic volume.
>>> On Jun 7, 2018, at 03:57, segs <michaelolusegunrufai at gmail.com> wrote:
>>> Hello All,
>>> Please I have a very interesting scenario that I am on the lookout for a
>>> solution for, We have instances where the network team of my company bypass
>>> controls and processes when adding new switches to the network.
>>> The right parameters that are required to be configured on the switches
>>> inorder for the NAC solution deployed to have full visibility into end
>>> points that connects to such switches are not usually configured.
>>> This poses a problem for the security team as they dont have visibility
>>> into such devices that connect to such switches on the NAC solution, the
>>> network guys usually connect the new switches to the trunk port and they
>>> have access to all VLANs.
>>> Is there a solution that can detect new or unmanaged switches on the
>>> network, and block such devices or if there is a solution that block users
>>> that connect to unmanaged switches on the network even if those users have
>>> domain PCs.
>>> Anticipating your speedy response.
>>> Thank You!
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