Command Line
fsianycpu.exe c:\path\to\test.fsscript
Description
Execute an arbitrary F# source-code files, bypassing WDAC policies for signed-binary execution.
Risk
High
Risk Reason
F# is suspicious on it's own for most users and is uncommon even for developers.
Fidelity
High
Fidelity Reason
This is unlikely to be a normal activity for most users, even developers. Consider alerting on non-standard arguments.
Operating Systems
Killchain Phases
References
MITRE ATT&CK TECHNIQUES
URL: https://attack.mitre.org/techniques/T1059
Description: Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries. These interfaces and languages provide ways of interacting with computer systems and are a common feature across many different platforms. Most systems come with some built-in command-line interface and scripting capabilities, for example, macOS and Linux distributions include some flavor of [Unix Shell](https://attack.mitre.org/techniques/T1059/004) while Windows installations include the [Windows Command Shell](https://attack.mitre.org/techniques/T1059/003) and [PowerShell](https://attack.mitre.org/techniques/T1059/001).
There are also cross-platform interpreters such as [Python](https://attack.mitre.org/techniques/T1059/006), as well as those commonly associated with client applications such as [JavaScript](https://attack.mitre.org/techniques/T1059/007) and [Visual Basic](https://attack.mitre.org/techniques/T1059/005).
Adversaries may abuse these technologies in various ways as a means of executing arbitrary commands. Commands and scripts can be embedded in [Initial Access](https://attack.mitre.org/tactics/TA0001) payloads delivered to victims as lure documents or as secondary payloads downloaded from an existing C2. Adversaries may also execute commands through interactive terminals/shells, as well as utilize various [Remote Services](https://attack.mitre.org/techniques/T1021) in order to achieve remote Execution.(Citation: Powershell Remote Commands)(Citation: Cisco IOS Software Integrity Assurance - Command History)(Citation: Remote Shell Execution in Python)
Tactics:
URL: https://attack.mitre.org/techniques/T1218
Description: Adversaries may bypass process and/or signature-based defenses by proxying execution of malicious content with signed, or otherwise trusted, binaries. Binaries used in this technique are often Microsoft-signed files, indicating that they have been either downloaded from Microsoft or are already native in the operating system.(Citation: LOLBAS Project) Binaries signed with trusted digital certificates can typically execute on Windows systems protected by digital signature validation. Several Microsoft signed binaries that are default on Windows installations can be used to proxy execution of other files or commands.
Similarly, on Linux systems adversaries may abuse trusted binaries such as split to proxy execution of malicious commands.(Citation: split man page)(Citation: GTFO split)
Tactics: