![]() ![]() Note that before you implement AppLocker rules in a production environment it is important to perform thorough testing. The AppLocker requirements can be found here. Note that it’s only available for particular editions, for example in Windows 10 you need Enterprise edition to make use of AppLocker. AppLocker takes the approach of denying all executables from running unless they have specifically been whitelisted and allowed.ĪppLocker is available in Windows Server 2008 R2 and newer, and Windows 7 Enterprise edition or newer on the client side. Please feel free to contact me or leave a message if you have any other questions/comments.We can implement AppLocker rules using group policy in a Windows domain to limit the execution of arbitrary executable files. Well folks, that covers interesting code execution and AppLocker bypass vectors to incorporate into your red team/pen test engagements. ::winning() AppLocker Bypass Resourcesįor more information about AppLocker bypass techniques, I highly recommend checking out The Ultimate AppLocker Bypass List created and maintained by Oddvar Moe ( Also, these resources were very helpful while drafting this post: For completeness, here is the CL sequence: powershell -v 2 -ep bypass Success! As an unprivileged user, we proved that we could bypass Constrained Language mode by invoking PowerShell version 2 (Note: this must be enabled) and bypassed AppLocker by loading an assembly through CL_LoadAssembly.ps1. The user calls the funrun assembly method and spawns calc.exe: To bypass Constrained Language mode, the user invokes PowerShell v2 and successfully loads the assembly with a path traversal call to funrun.exe: However, Constrained Language mode prevented the user from calling the method in PowerShell (v5) as indicated in the following screenshot: Using CL_LoadAssembly, the user successfully loads the assembly with a path traversal call to funrun.exe. When called on the cmd line and PowerShell (v5), this was prevented by policy as shown in the following screenshot:įunrun.exe was also prevented by policy when ran under PowerShell version 2: Using a Windows 2016 machine with Default AppLocker rules under an unprivileged user context, the user attempted to execute funrun.exe directly. NET 2.0) that I called funrun.exe, which runs calc.exe via proc.start() if (successfully) executed: In order to test this method, I compiled a very basic program (assembly) in C# (Target Framework. Additionally, alluded to a bypass technique with CL_LoadAssembly in a Tweet posted a few years ago: He successfully discovered an AppLocker bypass through the use of loading assemblies within PowerShell by URL, file location, and byte code. While investigating CL_LoadAssembly, I found a very interesting write-up ( Applocker Bypass-Assembly Load) by that describes research conducted by Casey Smith ( during a presentation at SchmooCon 2015. **Big thanks to and for their help and analysis of CL_Invocation Analysis of CL_LoadAssembly.ps1 Still, CL_Invocation.ps1 may have merit within trusted execution chains and evading defender analysis when combined with other techniques. PowerShell Contrained Language Mode (in PSv5) prevented the execution of certain PowerShell code/scripts and Default AppLocker policies prevented the execution of unsigned binaries under the context of an unprivileged account. However, further research indicated that this technique did not bypass any protections with subsequent testing efforts. CL_Invocation.ps1 (or import-module CL_Invocation.ps1) Importing the module and using SyncInvoke is pretty straight forward, and command execution is successfully achieved through. While investigating this script, it was quite apparent that executing commands would be very easy, as demonstrated in the following screenshot: and CL_LoadAssembly.ps1 provides two functions (LoadAssemblyFromNS and LoadAssemblyFromPath) for loading. In particular, two subdirectories (\AERO) and (\Audio) contained two very interesting, signed PowerShell Scripts:ĬL_Invocation.ps1 provides a function (SyncInvoke) to execute binaries through. While hunting, I came across an interesting directory structure that contained diagnostic scripts located at the following ‘parent’ path: %systemroot%\diagnostics\system\ AppLocker, Device Guard, AMSI, Powershell ScriptBlock Logging, PowerShell Constraint Language Mode, User Mode Code Integrity, HIDS/anti-virus, the SOC, etc.), looking for ways to deceive, evade, and/or bypass security solutions have become a significant component of the ethical hacker’s playbook. With increased client-side security, awareness, and monitoring (e.g. Last week, I was hunting around the Windows Operating System for interesting scripts and binaries that may be useful for future penetration tests and Red Team engagements. ![]()
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