![]() In theory this could be a valid bypass if you create a signed msi file that the client trusts. The publisher part looks like this inside the rule. The rule named “(Default Rule) All digitally signed Windows Installer files” will allow every digitally signed Windows installer file to execute. In this section we encounter our first Publisher rule. The default Windows installer rules looks like this: These section is used to defined the rules around windows installer files (.msi. The reasoning for this rule I think is to prevent lockout for admins.ĪppLocker Default Windows installer rules This could be seen as a weakness, but if you are a local administrator on a Windows box, AppLocker is pretty easy to stop just by halting a service. This means that if you are a local administrator you are allowed to execute everything on that system. The third rule named “(Default Rule) All files” is actually a rule created only for the users that are local administrator on the system. But the rule means that everything under C:\windows is allowed to execute. The second rule named “(Default Rule) All files located in the Windows folder”, I will not cover in detail with screenshots. This is pretty straightforward to understand. Here is a screenshot of the important part: The complete AppLocker variable list can be found here: %PROGRAMFILES% actually refers to both “Program files” and “Program files(x86)” As you probably understand from the %PROGRAMFILES%\* path, it means that everything under programfiles can be executed. The important part to notice from this screenshot is that the everyone group is used. If we open the rule you can see that it is defined like this: I will not go over every rule in such detail, just this first rule. Let me show you the details behind the first rule just to give you the basics. The first rule named “(Default Rule) All files located in the Program Files folder” makes sure that everyone can execute any binary file located within “Program files” and “Program files(x86)”. The default executable rules looks like this: These section is used to defined the rules around binary files (.exe and. It is no problem doing this on a single host without a domain) ![]() (Note that the gif assumes that you are in a domain environment. If you are wondering how to create the Default AppLocker rules you can read the first part of this blogpost: But before we dive into rule making, let me first explain the default rules in detail. I will explain different methods of mitigating using AppLocker. In this post I will cover how to go beyond the default rules in AppLocker and harden it to prevent msbuild.exe from working. The next question is, how can we mitigate this to harden the default setup? In my post about how insecure AppLocker really are we concluded that the only valid bypass technique (from the 7 I tested) was actually msbuild.exe. Since I have learned so much stuff from that guy, I take these sort of request really seriously. This blogpost is actually a tribute to Matt Graeber’s request from twitter. ![]()
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