Scripting

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Scripting
Technique
ID T0853
Tactic Execution
Data Sources Process monitoring, File monitoring, Process command-line parameters
Asset Engineering Workstation

Description

Adversaries may use scripting languages to execute arbitrary code in the form of a pre-written script or in the form of user-supplied code to an interpreter. Scripting languages are programming languages that differ from compiled languages, in that scripting languages use an interpreter, instead of a compiler. These interpreters read and compile part of the source code just before it is executed, as opposed to compilers, which compile each and every line of code to an executable file. Scripting allows software developers to run their code on any system where the interpreter exists. This way, they can distribute one package, instead of precompiling executables for many different systems. Scripting languages, such as Python, have their interpreters shipped as a default with many Linux distributions.

In addition to being a useful tool for developers and administrators, scripting language interpreters may be abused by the adversary to execute code in the target environment. Due to the nature of scripting languages, this allows for weaponized code to be deployed to a target easily, and leaves open the possibility of on-the-fly scripting to perform a task.


Procedure Examples

  • APT33 utilized PowerShell scripts to establish command and control and install files for execution.12
  • HEXANE utilizes VBA macros and Powershell scripts such as DanDrop and kl.ps1 tools.34
  • OilRig has embedded a macro within spearphishing attachments that has been made up of both a VBScript and a PowerShell script.5
  • In the version of Triton available at the time of publication, the component that programs the Triconex controllers is written entirely in Python. The modules that implement the communication protocol and other supporting components are found in a separate file -- library.zip -- which the main script that employs this functionality is compiled into a standalone Windows executable -- trilog.exe -- that includes a Python environment.6
  • A Python script seen in Triton communicates using four Python modules—TsBase, TsLow, TsHi, and TS_cnames—that collectively implement the TriStation network protocol (“TS”, via UDP 1502); this is the protocol that the TriStation TS1131 software uses to communicate with Triconex safety PLCs.6

Mitigations

  • Application Isolation and Sandboxing - Consider the use of application isolation and sandboxing to restrict specific operating system interactions such as access through user accounts, services, system calls, registry, and network access. This may be even more useful in cases where the source of the executed script is unknown.
  • Disable or Remove Feature or Program - Consider removal or disabling of programs and features which may be used to run malicious scripts (e.g., scripting language IDEs, PowerShell, visual studio).
  • Execution Prevention - Execution prevention may prevent malicious scripts from accessing protected resources.