I have had Bro installed as my gateway for a home network for about nine months now, with a complete (mostly uninterrupted) run of logs. I’ve also supplemented this with the critical stack plugin since July, with intel feeds up - focused mostly on malware and candc domains.
The network is reasonably busy, has probably about 25 discreet hosts of which at any given time between 3 and 10 are up. I have suspected there is malware / a rootkit perhaps on the network for a while as arp -a shows a lot of hosts every now and then from the terminal of most systems on the network. Also, Nmap scans often report IP addresses that simply are not there.
Also, Bro reports traffic to local NAT IP addresses that don’t exist. eg my network is divided into a 192.168.2.x (Internal, all the hosts) and 192.168.1.x(airgap between Bro router and domestic DSL router). The 192.168.1.x network only really ever has two hosts - the bro router and the dsl router, but connections show to other addresses which don’t exist.
I have tried to put a methodology together for malware hunting based on what I can find online, but nothing has really come to light. I use zcat, bro-cut and regular expressions to query the logs.
Would anyone on this list mind assisting me in a bug hunt / provide a methodology for tracking down suspicious traffic?
I have looked and looked but can’t seem to find any workflow / tolling which can isolate malware effectively. Any advice on this would be very gratefully received!