Detect Visual Basic in Google Chronicle
Adversaries may abuse Visual Basic (VB) for execution. VB is a programming language created by Microsoft with interoperability with many Windows technologies such as COM and the Native API. Derivative languages include Visual Basic for Applications (VBA) embedded in Microsoft Office documents and VBScript executed via Windows Script Host (wscript.exe/cscript.exe). VBA macros in Office documents remain one of the most prevalent initial access vectors, while VBScript is used in HTA files and standalone scripts for payload delivery and execution.
MITRE ATT&CK
- Tactic
- Execution
- Technique
- T1059 Command and Scripting Interpreter
- Sub-technique
- T1059.005 Visual Basic
- Canonical reference
- https://attack.mitre.org/techniques/T1059/005/
YARA-L Detection Query
rule t1059_005_vbscript_suspicious_execution {
meta:
author = "Argus Detection Engineering"
description = "Detects suspicious execution of wscript.exe, cscript.exe, or mshta.exe with VBScript/HTA indicators consistent with MITRE ATT&CK T1059.005 - Visual Basic"
mitre_attack_tactic = "Execution"
mitre_attack_technique = "T1059.005"
severity = "HIGH"
confidence = "HIGH"
events:
$e.metadata.event_type = "PROCESS_LAUNCH"
$e.principal.process.file.full_path = /(?i)(\\wscript\.exe|\\cscript\.exe|\\mshta\.exe)$/
(
re.regex($e.target.process.command_line, `(?i)(\.(vbs|vbe|wsf|hta))`)
or re.regex($e.target.process.command_line, `(?i)(createobject|wscript\.shell|shell\.application|scripting\.filesystemobject)`)
or re.regex($e.target.process.command_line, `(?i)(adodb\.stream|msxml2\.xmlhttp|winhttp\.winhttprequest)`)
or re.regex($e.target.process.command_line, `(?i)(winmgmts|win32_process|getobject)`)
or re.regex($e.target.process.command_line, `(?i)(powershell|cmd\s+/c|cmd\.exe)`)
or re.regex($e.target.process.command_line, `(?i)(\-decode|certutil|bitsadmin)`)
or re.regex($e.target.process.command_line, `(?i)(regwrite|regread|regdelete|environ\(|callbyname)`)
)
condition:
$e
}Chronicle YARA-L 2.0 rule detecting T1059.005 Visual Basic execution by matching wscript.exe, cscript.exe, and mshta.exe process launches with suspicious command-line arguments including shell object creation, network download COM objects, WMI execution, registry manipulation, and encoded payload delivery chains.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate enterprise build pipelines or CI/CD systems that invoke VBScript-based test harnesses or build steps via wscript.exe
- Active Directory Group Policy scripts executed at logon/logoff via wscript.exe targeting network shares
- Third-party monitoring agents (e.g., SolarWinds, Nagios) that use VBScript-based health check scripts to query WMI metrics
Other platforms for T1059.005
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1VBScript Execution via wscript.exe
Expected signal: Sysmon Event ID 1: Process Create for wscript.exe with the .vbs file path. Child process event for cmd.exe spawned by wscript.exe. Sysmon Event ID 11: File Create for the .vbs file.
- Test 2MSHTA Inline VBScript Execution
Expected signal: Sysmon Event ID 1: Process Create for mshta.exe with 'vbscript:Execute' in CommandLine. Child process creation for calc.exe spawned by mshta.exe.
- Test 3VBScript Network Download via XMLHTTP
Expected signal: Sysmon Event ID 1: Process Create for cscript.exe. Sysmon Event ID 3: Network Connection to 127.0.0.1:8080. AMSI Event: VBScript content inspection may trigger.
References (5)
- https://attack.mitre.org/techniques/T1059/005/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1059.005/T1059.005.md
- https://techcommunity.microsoft.com/t5/microsoft-365-blog/helping-users-stay-safe-blocking-internet-macros-by-default-in/ba-p/3071805
- https://lolbas-project.github.io/lolbas/Binaries/Mshta/
- https://github.com/SigmaHQ/sigma/tree/master/rules/windows/process_creation
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