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Command and Scripting Interpreters

As cyber defenders, we need to understand the techniques attackers use to compromise systems. One very common and powerful technique is abusing command and scripting interpreters. Let's break this down.

What are Command and Scripting Interpreters?

These are programs that allow you to execute instructions/commands on an operating system. Some examples:

  • Windows Command Prompt (cmd.exe)
  • PowerShell (powershell.exe)
  • Bash shell on Linux/macOS
  • Python (python.exe)
  • Perl (perl.exe)

While intended for legitimate tasks, hackers love these interpreters because of their versatility during attacks.

How Attackers Abuse Them

Interpreters provide functionality to perform all sorts of malicious actions like:

  • Running code to activate malware
  • Harvesting user credentials
  • Scanning/reconnaissance of networks
  • Lateral movement to other systems
  • Data destruction

For example, an attacker may use cmd.exe or PowerShell to run utilities like net.exe to find other machines to attack. Or they may run scripts to download more hacking tools.

Mitigating the Risks

To limit attackers abusing interpreters:

  • Use whitelisting to only allow approved interpreters to run
  • Restrict permissions to only give authorized people/programs access
  • Configure PowerShell to prevent unsigned/malicious scripts
  • Use security tools to watch for anomalous interpreter behavior

Detecting the Technique

Signs an interpreter may be abused include:

  • Unexpected interpreters like cmd.exe running
  • Interpreters spawning other suspicious programs
  • Network connections initiated by interpreters
  • Interpreters being leveraged to run recon/scanning commands

Logging tools like Sysmon can record interpreter execution. EDR solutions can detect and prevent malicious interpreter activity.

The flexibility of interpreters is why attackers rely on them so heavily. By understanding this technique, defenders can take steps to shut down this attack vector.

Let me know if you need any clarification or have additional suggestions for this blog post draft!

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