this search might be prone to high false positives. please consider this when conducting analysis or investigations. authorized devices may be detected as unauthorized. if this is the case, verify the mac address of the system responsible for the false positive and add it to the assets and identity framework with the proper information.

Techniques

Sample rules

Detect Unauthorized Assets by MAC address

source: splunk
technicques:

Description

By populating the organization’s assets within the assets_by_str.csv, we will be able to detect unauthorized devices that are trying to connect with the organization’s network by inspecting DHCP request packets, which are issued by devices when they attempt to obtain an IP address from the DHCP server. The MAC address associated with the source of the DHCP request is checked against the list of known devices, and reports on those that are not found.

Detection logic


| tstats `security_content_summariesonly` count from datamodel=Network_Sessions where nodename=All_Sessions.DHCP All_Sessions.tag=dhcp by All_Sessions.dest_ip All_Sessions.dest_mac 
| dedup All_Sessions.dest_mac
| `drop_dm_object_name("Network_Sessions")`
|`drop_dm_object_name("All_Sessions")` 
| search NOT [
| inputlookup asset_lookup_by_str 
|rename mac as dest_mac 
| fields + dest_mac] 
| `detect_unauthorized_assets_by_mac_address_filter`