I'm searching for a equivalent of "iwconfig eth0 mode Monitor" in Mac OS.
From man iwconfig mode Monitor does the following:
"the node is not associated with any cell and passively monitor all packets on the frequency"
What you're looking for is
Example of sniffing in monitor mode:
This sniffs on channel 1 and saves a pcap capture file to
To search for active channels nearby that you can sniff, run this:
Although you can capture any traffic, you can only effectively read if the network is open or you have the encryption key.
You can also do it via the GUI if that is easier for you.
Pass the -I flag to tcpdump or tshark (wireshark command-line utility).
For example, to save everything from radiotap headers down to the application layer packets to a file named 'save.pcap':
Or to examine probe request 802.11 management frames live:
Note, one OS X you will have to run the commands as root or grant yourself permission to access the kernel's packet filters:
by default on OSX en0 is your ethernet port, while en1 is your airport