Sniffing on the wire


suppose I have vlan-10  

I have a webserver with IP

An attacker is able to compromise physical security and plug his laptop into vlan10 and get IP address  The attacker then runs wireshark and starts sniffing on that interface.
The attacker has no access to the cisco switch to span traffic to his machine.

Question, given what I stated above is there anyway the attacker can see traffic from anywhere destined to the webserver?  He should only be able to see broadcast and multicast traffic but not unicast.
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Zephyr ICTCloud ArchitectCommented:
There's a lot of if's and but's that we will ignore for now, so in theory yes, that should be the case.

But there's always some kind of unicast that can leak out over other ports, thinking about mac-addressing aging out, NLB (Microsoft), asymmetric routing issues and so on ... So it's not that the attacker will see broadcast/multicast only network traffic, there might be some (albeit not a lot) unicast in there.

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Rich RumbleSecurity SamuraiCommented:
Arp poisioning will allow the attacker to get additional traffic, but it's not a useful as it used to be. Cain &Abel has arp poisioning built in. CAM table overflow used to be another good technique, but cisco has mitigations for that now:
JohnBusiness Consultant (Owner)Commented:
If the attacker is knowledgeable and could find a way to install Comm View Remote Agent on your system, then they can span networks with Comm View (a very good packet sniffer).
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Michael OrtegaSales & Systems EngineerCommented:
Suppose the attacker scanned the subnet and obtained the IP/MAC of your webserver. Could he not then spoof the MAC of the webserver and, as a result, absorb some or a lot of the traffic originally intended for the legitimate webserver? If he has physical access, couldn't he then just disconnect the webserver all together and see all traffic that was originally intended for the webserver?

Dave HoweSoftware and Hardware EngineerCommented:
Depends also what you mean by "compromised physical security".

Best way to intercept traffic for a given port on a switch if you have physical access to the switch port or wall port is layer two bridging - on a linux pc with two network cards, set up a BR0 interface bridging the two network cards, then place it physically inline between the switch and the webserver.  the linux host will bridge the two cards (so the switch will still see the mac address of the webserver, not that of the linux machine, and can still negotiate any port security that is in place) but the traffic is exposed to the linux host and can either be captured, or even MitM'd with the right filter rules and appropriate daemons (for instance, you can transparently MitM SSL connections, although if you have to spoof the certificate it may well trigger an error at the client side)
trojan81Author Commented:
appreciate it folks
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