Full Report
Sally Vandeven // We have all heard people talk about how much cooler Linux is than Windows, so much easier to use, etc. Well, they are not necessarily wrong… but we […] The post Rainy Day Windows Command Research Results appeared first on Black Hills Information Security, Inc..
Analysis Summary
# Main Topic
Research into built-in Windows command-line utilities that exhibit "Linux-like" functionality, focusing on how these "Living off the Land" (LOTL) tools can be leveraged by penetration testers while also providing defensive considerations for blue teams.
## Key Points
- Microsoft is integrating Linux-like functionality into Windows (e.g., WSL).
- The reviewed utilities offer versatile capabilities for file manipulation, encoding/decoding, network interaction, and system enumeration, often avoiding standard security scrutiny.
- Specific utilities like `certutil` (for base64/hex encoding/decoding), `clip` (for clipboard redirection), `curl` (for command-line web transfers), and `tar` (for archiving/compression) mimic common Linux tools.
- The `net1` command is highlighted as a potentially less monitored alternative to the standard `net` command for system enumeration.
## Threat Actors
- Not explicitly linked to a specific named threat actor, but these techniques are primarily presented as beneficial for **Pentesters** and potential **Adversaries** employing LOTL strategies.
## TTPs
- **Data Staging/Evasion (Encoding/Decoding):** Using `certutil` to base64 encode/decode executables to bypass network controls that scan for EXE files.
- **Data Exfiltration/Collection:** Redirecting command output directly to the clipboard using `clip` for easy data gathering or retrieval (e.g., `net1 start | clip`).
- **Network Operations:** Utilizing `curl` to download content, potentially bypassing proxies logging standard browser downloads.
- **System Enumeration (Less Monitored):** Employing `net1` instead of `net` to query services or local groups, aiming to evade detection rules focused on the standard `net` binary.
- **System Administration/Discovery:** Using `wslconfig` to determine if Windows Subsystem for Linux (WSL) distributions are installed.
## Affected Systems
- **Operating Systems:** Windows 10 builds (specifically those with WSL functionality integrated).
- **Platforms:** Any Windows system leveraging these native commands for operational tasks.
## Mitigations
- **Monitoring Focus:** Blue teams should concentrate monitoring efforts on the execution of these specific utilities (`curl`, `certutil`, `tar`) as their usage by standard users is infrequent, making deviations actionable alerts rather than noise.
- **Credential Risk Awareness:** Be aware of the potential use of `cmdkey` for accessing stored credentials, although testing for privilege escalation via this method was inconsistent.
- **WSL Visibility:** Monitor for the presence and usage of the `wslconfig` command to identify if administrative rights allow for the installation/running of Linux distributions on the endpoint.
## Conclusion
The research emphasizes that many native Windows commands, especially those recently augmented with Linux-like features (like `curl` and `tar`), can be effectively used for "living off the land" operations. Defenders should profile the baseline usage of tools like `certutil` and `net1` within their environments to establish alerts for anomalous behavior, as these tools present a low-hanging fruit for adversaries seeking to operate covertly.