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Mimikatz Rapid Config

By Larry Howarth posted Jan 11, 2019 09:23 PM

  

What is Mimikatz

Mimikatz started life as a GitHub project by Benjamin Delpy to illustrate flaws within the Windows Authentication subsystem. It is a tool that can extract plain text passwords, NTLM hashes, Kerberos Ticket Granting Tickets (TGT), and more from memory.

Malicious actors have leveraged this technology to infiltrate environments and move laterally across systems using legitimate credentials...undetected. 

How can Cb Protection help?

An endpoint in default deny mode (or what we like to call High Enforcement) will be protected from a binary-based Mimikatz attack because the process used to launch the attack will not be approved and therefore blocked. 

Cb Protection can protect endpoints in other enforcement levels against binary and memory based attacks with the use of the Mimikatz Protection Rapid Config. 

Rapid Config Details

The Mimikatz Protection Rapid Config has three sections that look for different indicators of compromise.

The first section allows you to Report or Block on the detection of a combination of DLLs loading. This particular combination (samlib.dll, cryptdll.dll, and vaultcli.dll) is a good indication of a Mimikatz process as these are not typically loaded at the same time by other processes.

 mimikat 1.png

 

As with all Rapid Configs we recommend setting each section to Report prior to setting to Block. You will want to ensure that the legitimate behavior of these dlls will not be impacted.

The second section of the Rapid Config looks for specific command lines. It will look for:

  • *sekurlsa* anywhere within the command line. Sekurlsa is a Mimikatz module that extracts passwords, keys, etc from the memory of lsass.
  • *privilege*debug* in the command line argument. The combination of “privilege” and “debug” within a command line argument is typically used by Mimikatz to get access rights.

mimikat 2.png

*These command line arguments can be changed by a malicious actor, we believe the default arguments will help catch low hanging fruit.

  

The final section of the Rapid Config centers on the reading of Lsass.exe memory. 

mimikat 3.png

Most processes should not be reading from lsass memory, however there are executables that legitimately need to do this. Out of the box we’ve included processes like ntoskrnl.exe, msiexec.exe, svchost.exe, and others that should be allowed to read the memory. 

It is crucial to initially set this section to Report so that you can find that approved applications in your environment that legitimately need to read the lsass process memory. After letting the Rapid Config run in Report mode for a few weeks, add any approved processes that access lsass memory to the exception list.

 

 


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