A small discovery about AppLocker

While I was prepping for a session a while back I made a a little special discovery about AppLocker. Turns out that the files that AppLocker uses under C:\Windows\System32\AppLocker can be used in many cases to bypass a Default AppLocker ruleset. When a machine is deployed and the first user logs in, that user will … Continue reading A small discovery about AppLocker

Bypassing AppLocker as an admin

I thought it would be useful to have a blog post about two different techniques you can use to bypass AppLocker if you are an admin on a host that has AppLocker enabled. The first technique that uses the GUI was briefly discussed in a tweet I posted a while back: https://twitter.com/Oddvarmoe/status/996147947975962624  My goal with this … Continue reading Bypassing AppLocker as an admin

%Temp%orary Constrained Language mode in AppLocker

TL;DR Done as a normal user without admin privs Change %TEMP%/%TMP% to point to a location that allows execution of scripts defined by AppLocker Start Powershell with the new environment variables that you set for %TEMP%/%TMP% and profit! Background This blogpost covers a technique I discovered when digging further into AppLocker to bypass Powershell Constrained … Continue reading %Temp%orary Constrained Language mode in AppLocker

Persistence using Universal Windows Platform apps (APPX)

TL;DR Persistence can be achieved with Appx/UWP apps using the debugger options. This technique will not be visible by Autoruns. Two different approaches exists (registry keys). Listed below are the two techniques for two different apps that starts at logon: Cortana app: reg add HKCU\Software\Microsoft\Windows\CurrentVersion\PackagedAppXDebug\Microsoft.Windows.Cortana_1.10.7.17134_neutral_neutral_cw5n1h2txyewy /d "C:\windows\system32\cmd.exe" OR reg add HKCU\Software\Classes\ActivatableClasses\Package\Microsoft.Windows.Cortana_1.10.7.17134_neutral_neutral_cw5n1h2txyewy\DebugInformation\CortanaUI.AppXy7vb4pc2dr3kc93kfc509b1d0arkfb2x.mca /v DebugPath /d "C:\windows\system32\cmd.exe" … Continue reading Persistence using Universal Windows Platform apps (APPX)

Windows Defender Attack Surface Reduction Rules bypass

I discovered an easy way to bypass the Windows Defender Attack Surface Reduction Rules using code inside a macro. This issue has already been fixed with the Windows Defender virus definition version: 1.263.536.0 and above. I was first told to report this to secure@microsoft.com, but it turns out that these kinds of bypasses are considered … Continue reading Windows Defender Attack Surface Reduction Rules bypass

Putting data in Alternate data streams and how to execute it

Part 2 of this research can be found here: https://oddvar.moe/2018/04/11/putting-data-in-alternate-data-streams-and-how-to-execute-it-part-2/ I always had a fascination about ADS (Alternate data streams) and using it as part of a persistence. My first meeting with this as a persistence technique was when Matt Nelson aka @Enigma0x3 wrote a blogpost about using it: https://enigma0x3.net/2015/03/05/using-alternate-data-streams-to-persist-on-a-compromised-machine/ Quite recently I have started to play … Continue reading Putting data in Alternate data streams and how to execute it

Bypassing Device guard UMCI using CHM – CVE-2017-8625

TL;DR You could/can bypass Device Guard user mode code integrity with a custom CHM and execute code.   The last 6 months I have done some security research on my (little) spare time, because I find that very interesting. During this time, I was lucky enough to find another valid Device Guard UMCI bypass (I … Continue reading Bypassing Device guard UMCI using CHM – CVE-2017-8625

Clarification – BGInfo 4.22 – AppLocker still vulnerable

Just wanted to do a quick follow-up on this bypass. Seems that BGInfo 4.22 still can be used to bypass AppLocker using the techniques I showed in my previous post. Meaning that if you use AppLocker as whitelisting solution I guess you must deny BGInfo.exe in order to prevent this bypass. Screenshots from an AppLocker … Continue reading Clarification – BGInfo 4.22 – AppLocker still vulnerable

Bypassing Application Whitelisting with BGInfo

TL;DR BGinfo.exe older than version 4.22 can be used to bypass application whitelisting using vbscript inside a bgi file. This can run directly from a webdav server.   UPDATE: 22.05.2017 AppLocker is still vulnerable with Bginfo 4.22. A blogpost about that here: https://msitpros.com/?p=3860 UPDATE: 19.06.2017 Microsoft has thanked me in their documentation for this finding. The … Continue reading Bypassing Application Whitelisting with BGInfo