Pen Testing

Intro to Mimikatz

One of the most interesting tools in a penetration tester’s arsenal is mimikatz.  Mimikatz is a tool that scrapes the memory of the process responsible for Windows authentication(LSASS) and reveals cleartext passwords and NTLM hashes that an attacker can use to pivot around a network.  From that point they escalate privilege either by authenticating with the clear text credentials or passing the hash. Sounds deadly right? Most people have the reaction “Why hasn’t Microsoft come up with a solution to this?”.

If you Google the phrase “defending against mimikatz” the information you find is a bit lackluster. The best article I have found was this one. It has a lot of good suggestions like using the “Protected Users” group(SID: S-1-5-21-<domain>-525) available in recent versions of Active Directory and also limiting administrator usage, and taking advantage of not storing passwords in memory with a registry setting. You can limit the number of services running as system or remove debug privilege to help prevent an attacker from being able to run mimikatz. What this and other articles make you believe is that you need to have Windows 8 or 8.1 or 10 rolled out everywhere. What about the large number of Windows 7/2008 R2 machines out there? Well it turns out you can defend against mimikatz on these versions of Windows, here is how. Read Full Article