With the number of attacks that we are facing today, defenders are looking for more and more IOC’s (“Indicator of Compromise) to feed their security solutions (firewalls, IDS, …). It becomes impossible to manage all those IOC’s manually and automation is the key. There are two main problems with this amount of data:
- How to share them in a proper way (remember: sharing is key).
- How to collect and prepare them to be shared.
Note that I’m considering in this post only the “technical” issues with IOC’s. There are much more issues like their accuracy (which can be different between different environments).
To search for IOC’s, I’m using the following environment: A bunch of honeypots capture samples that, if interesting, are analyzed by a Cuckoo sandbox. To share the results with peers, a MISP instance is used.
In this case, a proper integration between Cuckoo and MISP is the key. It is implemented in both ways. The results of the Cucko analyzis are enriched with IOC’s found in MISP. IOC’s found in the sample are correlated with MISP and the event ID, description and level are displayed:
In the other way, Cuckoo submits the results of the ianalyzes to MISP:
Cuckoo 2.0 comes with ready-to-use modules to interact with the MISP REST API via the PyMISP Python module. There is one processing module (to search for existing IoC’s in MISP) and one reporting module (to create a new event in MISP). The configuration is very simple, just define your MISP URL and API key in the proper configuration files and you’re good to go:
# cd $CUCKOO_HOME/conf # grep -A 2 -B 2 misp *.conf processing.conf-enabled = yes processing.conf- processing.conf:[misp] processing.conf-enabled = yes processing.conf:url = https://misp.xxxxxxxxxx processing.conf-apikey = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx maxioc = 100 -- reporting.conf-logname = syslog.log reporting.conf- reporting.conf:[misp] reporting.conf-enabled = yes reporting.conf:url = https://misp.xxxxxxxxxx reporting.conf-apikey = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
But, in my environment, the default modules generated too many false positives in both ways. I patched them to support the more configuration keywords to better control what is exchanged between the two tools.
In the processing module:
only_ids = [yes|no]
If defined, only attributes with the “IDS” flag set to “1” will be displayed in Cuckoo.
ioc_blacklist = 126.96.36.199,188.8.131.52,www.google.com
This parameter allows you to define a list (comma delimited) of IOC’s that you do NOT want in Cuckoo. Typically, you’ll add here DNS servers, specific URLs.
In the reporting module:
tag = Cuckoo
Specify the tag to be added to created event in MISP. Note that the tag must be created manually.
# Default distribution level: # your_organization = 0 # this_community = 1 # connected_communities = 2 # all_communities = 3 distribution=0
The default distribution level assigned to the created event (default: 0)
# Default threat level: # high = 1 # medium = 2 # low = 3 # undefined = 4 threat_level_id=4
The default threat level assigned to the created event (default: 4)
# Default analysis level: # initial = 0 # ongoing = 1 # completed = 2 analysis = 0
The default analysis status assigned to the created event (default: 0)
ioc_blacklist = 184.108.40.206,220.127.116.11,www.google.com,crl.verisign.com,sc.symcb.com
Again, a blacklist (comma separated) of IOC’s that you do NOT want to store in MISP.
Events are created in MISP with an “unpublished” status. This allows you to review them, add manually some IOC’s, to merge different events, add some tags or change default values.
The patched files for Cuckoo are available in my GitHub repository.