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Refreshing EK Hunting Technique (Enrichment) via TTP

Jan
02

Happy new year!

It has been a while since the last update.

Today I’ve saw an update in malware-traffic-analysis on RIG EK. Nothing new, but i asked myself if my old hunting technique is still relevant today, since i left EK hunting ‘industry’ 1 year++ ago. So i wrote a simple script to perform a quick check:

xanda:tmp xanda$ ./loop.sh 109.234.36.0
109.234.36.133
109.234.36.210
DONE!

I’ve found 2 IPs; 109.234.36.133 (currently serving RIG, mentioned in malware-traffic-analysis blog) and 109.234.36.210. 109.234.36.210 is not yet serving anything malicious, but my prediction, it will be serving RIG EK in/within the next 7 days.

Some tips on this fingerprinting technique:

  1. Based on the initial IP found, look for the IP range assigned to the same ASN, in this case 109.234.36.0/24
  2. Identify the HTTP header response from the known bad IP, and use it to fingerprint the rest.
  3. Based from my experience, 1 batch of EK server setup will have similar (or almost similar) HTTP header response, and some EK will use 1 subnet for 1 batch (but not necessarily)
  4. EK server will always (mostly) be dedicated. If you found historical pDNS record on that IP, verify (with dig/nslookup) for the current IP resolved by the domain(s). For example; 109.234.36.210 has 3 historical pDNS record, but at the moment, 1 of the domain has expired, and another 2 domains are now pointing to different IP(s).
  5. This method will only works if the “scanned” hosts are alive at that particular moment

Hope it helps. Happy hunting