Mitigating vulnerabilities with identity security posture assessments

Published Sep 03 2020 04:02 AM 4,395 Views
Microsoft

Imagine the following scenario, after a successful phishing campaign, an attacker finds themselves with an active shell on one of your non-sensitive employee’s devices. Using Living-off-the-Land (LotL) tactics (employing built in tools and commands), the attacker starts identifying their next targets and configuration weaknesses to leverage to comprise them. One such vulnerability might be the infamous print spooler bug.

 

The print spooler bug…

As published on the security conference DerbyCon at (2018), the print spooler bug is a way to gain elevated credentials (a sensitive computer account Kerberos ticket in this case) by exploiting two distinct configurations.

  1. A privileged device with the “print spooler” service running.
  2. A victim device configured for Unconstrained Kerberos delegation.

Using these two configurations in tandem, an attacker can “request” the sensitive device Kerberos ticket using the print spooler service through the victim’s device; and because unconstrained Kerberos delegation is enabled, that request will contain the highly sought-after Kerberos authentication ticket (TGT) that allows the attacker to impersonate the domain controller computer account - pretty bad, right?

 

1 Print spooler bug.png

*Image from https://adsecurity.org/?p=4056

 

What can you do?

As part of Azure ATP, we introduced the Identity Security Posture assessment that automatically looks for these kinds of risky configurations in your on-premises environment. This assessment and the recommendation are now integrated in Microsoft Secure Score, makes creating a mitigation plan for these recommended actions easier than ever. To view the recommendations you can use the following steps:

 

  1. Go to the Microsoft Secure Score portal.
  2. Use filters to show the relevant product or tags.sc.png

     

  3. Locate the relevant improvement actions for mitigating the print spooler bug, create an action plan using the built-in options or click “Manage to find out which entities have risky configurations and what actions are needed to re-configure them to remediate the issue.
 

3 Secure Score controls.png

 

Once mitigated, Microsoft Secure Score will reflect the actions taken by increasing your score and mark these improvement actions as “Completed”.

 

Now, let’s consider another scenario.

 

After mitigating the print spooler bug , you discover another improvement action called “Stop clear text credential exposure”. After clicking the “Manage” button to access the assessment to view additional details, you discover that a sensitive entity and an accompanying device are authenticating over LDAP simple bind. To make matters even worse, the exposed user is also sensitive (belonging to the Domain admin group)

 

4 LDAP Cleartext report.png

 

You then realize that if an attacker can get onto your network, they can “sniff” the transmitted credentials that are in clear text and gain elevated credentials.

To further investigate this case, you will need additional details regarding this type of unsecure communication such as:

  • What processes are causing this behavior?
  • Are any of them part of a critical application?
  • What should I do next?

The hunt is on…

To answer these questions, let’s utilize one of MTP’s cool features called Advanced hunting which is now also enriched with Azure ATP activities alongside other security products such as Microsoft Defender ATP, Cloud App Security and Azure AD, and data from Office 365.

We’ll start by going to the Advanced hunting page in the new M365 security portal and from there, we now have access to all the different types of hunting data available for us, including two main tables relevant for this task:

  1. IdentityLogonEvents – all logon events generated by Azure ATP including the LDAP Cleartext type
  2. DeviceNetworkEvents – All networking events generated by Microsoft Defender ATP including LDAP queries generated toward the domain controllers using port 389.

To get started, we can write a query, joining detected logon sessions and network events from both these tables, resulting in a consolidated result that includes the all the unsecure logon activities and their initiating process names.

 

5 Advanced Hunting.png

 

Using the query result, we can construct a cohesive story:

On Aug 05, Testuser2 used the LDP.exe executable to generate an unsecure authentication using LDAP Simple Bind from Client5.”

We now have the relevant details to create a full remediation plan for this activity, such as simply blocking LDP.exe or configuring the application to require a more secure authentication while blocking insecure authentications at the domain level.

 

Conclusion

And there you have it! Using Azure ATP’s Identity Security Posture assessment with Microsoft Secure Score and Advanced hunting, we can build a simple mitigation plan for our organization’s security weak spots, making it that much harder for the bad guy to get in

 

 

For more information about Identity Security Posture assessments and MTP, see

* Learn more about Identity security posture assessments.

* Learn more about Microsoft Secure Score

* Azure ATP activities in advanced hunting

 

Or Tsemah, Senior Product Manager, Azure ATP.

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