I have a "black-box device" (a credit card reader, to which some klutz lost the admin unlock card...) running an unknown, but primitive, operative system. I need to find it's MAC address.
At my disposal, I have the device itself (but no access to its admin interface), a computer running Ubuntu 12.04 (where I have full sudo rights), and a regular ethernet cable. If necessary, I can probably shake up an ethernet switch, too.
How do I go about to find the MAC address of the card reader?
By the help of a friend, I now resolved this! =) This is what I did:
Install Wireshark, which is available in the software repositories: sudo apt-get install wireshark
Start the program with root permissions: sudo wireshark
Start capturing on the eth0 device (piece of cake - click the button on the top left of the interface, select the device in the dialog and click OK).
Connect the "black-box device" and turn it on. The devices will send a large amount of packages back and forth trying to establish a connection. Wireshark will capture them all.
Find a packet originating from the "black-box device". Wireshark displays the originating MAC address. Voila!
If it does connect, nmap can perform a scan.
sudo nmap -PN 169.154.0.0/16
Also, more obscurely, if the device has a serial port you may get it to spill its guts on boot, and this might reveal static ip details as well.
Granted, this requires a cable, and guessing or obtaining the protocol attributes.
