You likely want DNS running on your Darknet server. In our example we will use the management servers 192.168.1.9 and 192.168.2.9 as our DNS name servers (they also serve NTP). Be careful with DNS and sniffing! Be sure to use the -n flag with tcpdump so that your Darknet server doesn't attempt to resolve each IP in your sniffer output. Our /etc/resolv.conf file should now include:
We're now going to add some software to our Darknet server. We use and recommend the following:
Argus
tcpdump
IP Filter
A discourse on how to build and implement each is beyond the scope of this treatise. Each comes with ample build and installation documentation. We will cover only certain tweaks here.
Argus and tcpdump should be configured to listen on the SNIFFER NIC only, in our example em0. The remote management daemon for Argus should be bound to the MGMT NIC only, e.g. fxp0, on port 2002 in our example. It should not be bound to the SNIFFER NIC.
Argus should be run as a daemon, and ideally started at boot. Here is a suggested template for your /etc/argus.conf file.
IP Filter should be configured to block everything in and out of the SNIFFER NIC interface. In our example this is the em0 interface, IP address 172.16.18.2. You may wish to log any hits on the block rules so that debugging and alerts are easy to accomplish; it's not a bad idea to do the same on the pass rules as well. If you choose to log the rule hits, remember to start ipmon with the proper flags.