Object ACLs

Each ACL has Access Control Entries (ACEs)—each one lists a user or group and their permissions (like read, write, or delete).

For example:

• Domain Admins can change any user’s password by default.

• Specific rights (like resetting passwords or modifying groups) can be delegated to other users.

ACLs also support auditing, such as tracking who accessed or tried to access an object.

In big organizations, mistakes happen, like:

• Regular users getting too many rights

• Everyone being able to change everything

• LAPS (local admin passwords) being visible to all

That’s why it's important to have clear rules and processes to manage access and remove rights when someone's role changes.

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Attack

To identify potential abusable ACLs, we will use BloodHound to graph the relationships between the objects and SharpHound to scan the environment and pass All to the -c parameter (short version of CollectionMethod)

1. First we obviously need to use the scan command

Scan AD enviroement

PS C:\Users\bob\Downloads> .\SharpHound.exe -c All

2022-12-19T14:16:39.1749601+01:00|INFORMATION|This version of SharpHound is compatible with the 4.2 Release of BloodHound
2022-12-19T14:16:39.3312221+01:00|INFORMATION|Resolved Collection Methods: Group, LocalAdmin, GPOLocalGroup, Session, LoggedOn, Trusts, ACL, Container, RDP, ObjectProps, DCOM, SPNTargets, PSRemote
2022-12-19T14:16:39.3468314+01:00|INFORMATION|Initializing SharpHound at 14.16 on 19/12/2022
2022-12-19T14:16:39.5187113+01:00|INFORMATION|Flags: Group, LocalAdmin, GPOLocalGroup, Session, LoggedOn, Trusts, ACL, Container, RDP, ObjectProps, DCOM, SPNTargets, PSRemote
2022-12-19T14:16:39.7530826+01:00|INFORMATION|Beginning LDAP search for eagle.local
2022-12-19T14:16:39.7999574+01:00|INFORMATION|Producer has finished, closing LDAP channel
2022-12-19T14:16:39.7999574+01:00|INFORMATION|LDAP channel closed, waiting for consumers
2022-12-19T14:17:09.8937530+01:00|INFORMATION|Status: 0 objects finished (+0 0)/s -- Using 36 MB RAM
2022-12-19T14:17:28.4874698+01:00|INFORMATION|Consumers finished, closing output channel
2022-12-19T14:17:28.5343302+01:00|INFORMATION|Output channel closed, waiting for output task to complete
Closing writers
2022-12-19T14:17:28.6124768+01:00|INFORMATION|Status: 114 objects finished (+114 2.375)/s -- Using 46 MB RAM
2022-12-19T14:17:28.6124768+01:00|INFORMATION|Enumeration finished in 00:00:48.8638030
2022-12-19T14:17:28.6905842+01:00|INFORMATION|Saving cache with stats: 74 ID to type mappings.
 76 name to SID mappings.
 1 machine sid mappings.
 2 sid to domain mappings.
 0 global catalog mappings.
2022-12-19T14:17:28.6905842+01:00|INFORMATION|SharpHound Enumeration Completed at 14.17 on 19/12/2022! Happy Graphing!

The ZIP file generated by SharpHound can then be visualized in BloodHound. Instead of looking for every misconfigured ACL in the environment, we will focus on potential escalation paths that originate from the user Bob (our initial user, which we had already compromised and have complete control over). Therefore, the following image demonstrates the different access that Bob has to the environment:

Bob has full rights over the user Anni and the computer Server01. Below is what Bob can do with each of these:

🔹 Case 1: Bob has full rights over user Anni

• Bob can change Anni’s password and log in as her. If Anni is a Domain Admin, Bob now has the same power.

• Bob can also add a Service Principal Name (SPN) to Anni’s account and then use Kerberoasting to try to crack the password.

🔹 Case 2: Bob has full rights over Server01 (a computer object)

• If LAPS is used, Bob can view the local admin password and log in as that account.

• Bob can also use Resource-Based Kerberos Delegation (RBCD) to impersonate any user when connecting to Server01.

• If Server01 is set for Unconstrained Delegation, and Bob controls it, he could steal credentials from Domain Controllers or other critical systems that connect to it — leading to privilege escalation.

We can also use ADACLScanner to create reports of discretionary access control lists (DACLs) and system access control lists (SACLs).

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Prevention

We can detect when AD objects are changed, but the logs don’t always show exactly what was changed.

For example, if Bob adds an SPN to Anni’s account (to later perform Kerberoasting), Windows will log Event ID 4738: "A user account was changed."

However, this event won’t show that an SPN was added — it just says the user was modified. So, while it's useful to know something changed, it lacks detail about what changed.

We can still spot suspicious actions by watching who made the change.

For example, if only admins have names like "adminXXXX", then any changes made by users without that naming pattern (like Bob) could be a red flag.

• If Bob resets someone’s password, Windows logs Event ID 4724.

• If Bob modifies a computer object (like Server01), Event ID 4742 is logged.

These events don’t show exact details, but they do show that something was done — and by whom. So, even if info is limited, they help detect misuse or abuse.

You can set up a honeypot user with high permissions and leak fake credentials (like in the description field). This could lure attackers to test the account.

Another method: create a honeypot user that anyone can modify. This account should look active but isn’t supposed to be changed.

• If Event ID 4738 appears for this user (showing a change), it’s suspicious.

• When detected, alert, disable the user who made the change, and start a forensic investigation.

For example, if Bob changes Anni’s account, this setup would catch it.