POWERSHELL SHENANIGANS KIERAN JACOBSEN HP ENTERPRISE SERVICES

WHAT IS POWERSHELL? Developed by Microsoft in 2006 Cross between a shell script and C# Replacement for VBScript Significant number of commands (called CMDLets) Runs on.NET Framework

CHALLENGE Move from social engineered workstation to domain controller Where possible use only PowerShell code Demo environment will be a “corporate like” environment

ADVANTAGES AS AN ATTACK PLATFORM Code is very easy to develop Windows integration Remote execution offerings Often overlooked by AV Easily hidden from administrators Installed by DEFAULT

MY POWERSHELL MALWARE Single Script – SystemInformation.ps1 Runs as a schedule task, every 5 minutes Script: Collects system information and more Connects to C2 infrastructure, downloads a task list and executes tasks Executes each task, if successful, task will not be rerun Tasks can be restricted to individual computers

DEMO: THE ENTRY

WINDOWS POWERSHELL REMOTING AND WINRM PowerShell Remoting is based upon WinRM, Microsoft’s WS-Management implementation Supports execution in 3 ways: Remote enabled commands Remotely executed script blocks Remote sessions Security Model = Trusted Devices + User Credentials WinRM is required for the Windows Server Manager As requested, you can find the slide deck here, and the GitHub code is available here. If you take a look through my GitHub repositories, you will notice how much PowerShell code I normally write, and you can also see the previous version of the same code.

DEMO: THE DC

POWERSHELL SECURITY FEATURES Administrative rights UAC Code Signing Local or Remote source using zone.identifier alternate data stream PowerShell Execution Policy

EXECUTION POLICY There are 6 states for the execution policy UnrestrictedAll scripts can run Remote SignedNo unsigned scripts from the Internet can run All SignedNo unsigned scripts can run RestrictedNo scripts are allowed to run Undefined (Default)If no policy defined, then default to restricted BypassPolicy processor is bypassed

BYPASSING EXECUTION POLICY Simply ask PowerShell: powershell.exe –executionpolicy unrestricted Switch the files zone.idenfier back to local:unblock-file yourscript.ps1 Read the script in and then execute it (may fail depending on script) Get/Steal a certificate, sign script, run script

DEMO: THE HASHES

OTHER CONSIDERATIONS PowerShell Web Access Desired State Configuration

LINKS AND QUESTIONS Blog: Code on GitHub: QuarksPWDump: PowerSploit: Microsoft PowerShell/Security Series: Practical Persistence in PowerShell: