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microsoft-workflow-compiler

A utility included with .NET that is capable of compiling and executing C# or VB.net code. Located at: C:\Windows\Microsoft.Net\Framework64\v4.0.30319\Microsoft.Workflow.Compiler.exe.

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microsoft-workflow-compiler
microsoft-workflow-compiler

Sandbox: execFile · Timeout: 30s

Capabilities

security.execution.command
security.defense-evasion.bypass

Contract

Outputs

process.output

Command execution output

Side effects: process_spawn

Workflow Edges

Produces

process.output

Resource Profile

ResourceValue
CPUlow
Memory16 MB
Networklow
Disk I/Olow

Examples

Compile and execute C# or VB.net code in a XOML file referenced in the first argument (any extension accepted). (Compile and run code)

Microsoft.Workflow.Compiler.exe {PATH} {PATH:.log}

Compile and execute C# or VB.net code in a XOML file referenced in the test.txt file. (Compile and run code)

Microsoft.Workflow.Compiler.exe {PATH} {PATH:.log}

Compile and execute C# or VB.net code in a XOML file referenced in the test.txt file. (Compile and run code)

Microsoft.Workflow.Compiler.exe {PATH} {PATH:.log}

Detection

TypeRule / Indicator
sigma https://github.com/SigmaHQ/sigma/blob/c04bef2fbbe8beff6c7620d5d7ea6872dbe7acba/rules/windows/process_creation/proc_creation_win_lolbin_workflow_compiler.yml
splunk https://github.com/splunk/security_content/blob/961a81d4a5cb5c5febec4894d6d812497171a85c/detections/endpoint/suspicious_microsoft_workflow_compiler_usage.yml
splunk https://github.com/splunk/security_content/blob/18f63553a9dc1a34122fa123deae2b2f9b9ea391/detections/endpoint/suspicious_microsoft_workflow_compiler_rename.yml
elastic https://github.com/elastic/detection-rules/blob/414d32027632a49fb239abb8fbbb55d3fa8dd861/rules/windows/defense_evasion_unusual_process_network_connection.toml
elastic https://github.com/elastic/detection-rules/blob/414d32027632a49fb239abb8fbbb55d3fa8dd861/rules/windows/defense_evasion_network_connection_from_windows_binary.toml
blockrule https://docs.microsoft.com/en-us/windows/security/threat-protection/windows-defender-application-control/microsoft-recommended-block-rules
ioc Microsoft.Workflow.Compiler.exe would not normally be run on workstations.
ioc The presence of csc.exe or vbc.exe as child processes of Microsoft.Workflow.Compiler.exe
ioc Presence of "<CompilerInput" in a text file.

Documentation

microsoft-workflow-compiler

microsoft-workflow-compiler is a Windows LOLBin. A utility included with .NET that is capable of compiling and executing C# or VB.net code. Located at: C:\Windows\Microsoft.Net\Framework64\v4.0.30319\Microsoft.Workflow.Compiler.exe.

References