Threat Hunting with Zeek (Bro) and MISP

This module uses Zeek's built-in Intelligence Framework to load and monitor signatures from MISP automatically. Indicators are downloaded from MISP every 4 hours and hits, called sightings, are reported back to MISP immediately. The module also includes a customized version of Jan Grashoefer's expiration code to remove indicators after they are deleted from MISP.

Indicators are downloaded and read into memory. Content signatures in signatures.sig are MISP Network Activity->zeek items downloaded from MISP. The event text should start with "MISP:" (see Sample Content Signature section for an example). Zeek must be restarted to ingest the content signatures. To do this automatically we recommend restarting Zeek using zeekctl and a restart cron described in included file INSTALL.md

Optional Slack.com web hook reporting.

signature eicar_test_content {
  ip-proto == tcp
  payload /.*X5O\!P%@AP\[4\\PZX54\(P\^\)7CC\)7\}\$EICAR\-STANDARD\-ANTIVIRUS\-TEST\-FILE\!\$H\+H\*/
  event "MISP: eicar test file in TCP plain text"
}

Note: Zeek's default setting is to buffer the first 1024 bytes of a TCP connection so signature's should be written with that in mind.

Indicators are downloaded automatically every 4 hours and are assigned an expiry of 4.5 hours. A check for expired indicators occurs every 4.5 hours to cleanup any expired indicators between downloads. As indicators are reingested the expiration time is reset to 4.5 hours. A message is now printed for each expired indicator.

If an indicator is hit after expiration but before the cleanup, it will trigger a hit/sighting, but the indicator is then deleted immediately so no further hits will occur.

Intervals are set in config.zeek.

redef Intel::item_expiration = 4.5 hr

global signature_refresh_period = 4hr &redef;

redef Intel::item_expiration = 4.5 hr;

global MAX_HITS: int = 100;

global MAX_DNS_HITS: int = 2;

global MAX_SCAN_HITS: int = 2;

global IGNORE_SNI_MISMATCH: bool = T;

https://dovehawk.io/

https://github.com/tylabs/dovehawk/

http://www.misp-project.org/ MISP

https://www.zeek.org/ Zeek Network Security Monitor

The entire MISP team and Alexandre Dulaunoy @adulau for adding the zeek datatype to MISP.

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