Unveiling the Shadows: Mastering Persistence Detection with…

Welcome, esteemed defenders. Today, we delve into the critical realm of persistence detection, a cornerstone of Digital Forensic and Incident Response (DFIR). In our previous exploration, we examined Windows persistence mechanisms, a vital skill for both red and blue teams. Today, we focus on the defensive side, equipping you with PowerShell tools to uncover hidden persistence mechanisms that adversaries might employ.

Persistence is a deceptive adversary’s best friend. It allows them to maintain a foothold in a compromised environment, even after initial detection and removal. A single persistence mechanism might not be enough; attackers often layer multiple techniques to ensure their access remains intact. We’ve encountered cases where incident responders removed scheduled tasks and services, only to find that forgotten credentials and remote-access tools like AnyDesk allowed attackers to re-enter days later. In other instances, attackers planted helper processes that resurrect payloads after removals. Therefore, treat every environment as potentially “radioactive.” Assume survivors exist and search for them meticulously.

To illustrate, we used a simple BootExecute persistence entry. BootExecute is a legacy Windows mechanism that runs specified commands very early during boot, before most services and user sessions. An adversary who replaces or extends this value can schedule executables to run before the system fully initializes. We confirmed that our BootExecute example indeed ran on boot, highlighting the potential threat posed by such mechanisms.

Now, let’s explore three powerful PowerShell tools designed to help you find similar persistence mechanisms across your estate.

Persistence Sniper

Repository: https://github.com/last-byte/PersistenceSniper

PersistenceSniper is a modern PowerShell module designed to enumerate known persistence locations and present them in an analyst-friendly format. It meticulously examines standard locations such as services, scheduled tasks, Run keys, Winlogon, Startup folders, WMI persistent subscriptions, AppInit DLLs, service image paths, and more. It returns structured results with context, flags suspicious items, and maps findings to ATT&CK techniques where appropriate.

Installation in 2023 may differ slightly from older documentation. Here’s a reliable installation approach:

“`
PS > powershell -ep bypass
PS > Install-Module -Name PersistenceSniper -Scope CurrentUser -Force -SkipPublisherCheck
PS > Import-Module PersistenceSniper
“`

Once imported, a single command scans the host:

“`
PS > Find-AllPersistence -Verbose
“`

The output is verbose and intentionally descriptive, providing a comprehensive view of the system’s persistence mechanisms. You will encounter entries for native system binaries in legitimate locations, but not everything is hostile. PersistenceSniper classifies findings and maps the BootExecute change to ATT&CK technique T1547.001, aiding in incident tagging and report generation.

Use PersistenceSniper as a first pass during triage on a live endpoint. It is fast, produces human-readable commentary, and is ideal for analysts who need to quickly determine whether a host still contains surviving persistence after an initial cleanup.

Trawler

Repository: https://github.com/joeavanzato/Trawler

Trawler approaches the same problem with a different emphasis. While PersistenceSniper aims to be comprehensive and explanatory, Trawler attempts to reduce noise and present only items that look like adversary persistence. This approach is useful when you are hunting at scale and do not want dozens of benign services getting in the way of triage. However, the trade-off is that Trawler can produce false negatives when an attacker deliberately mimics an allow-listed item. Always validate any findings manually, as a “no findings” result does not guarantee a clean system. Trawler also supports scanning offline images and mounted drives, a crucial feature during forensic acquisition. You can point Trawler at a drive and it will scan it thoroughly.

To install Trawler, follow these steps:

“`
PS > git clone https://github.com/joeavanzato/Trawler.git
PS > cd Trawler
PS > .\Trawler.ps1
“`

Once installed, you can run Trawler with the following command:

“`
PS > .\Trawler.ps1 -Scan
“`

Trawler’s output is concise and focused, highlighting potential persistence mechanisms that require further investigation. It is an excellent tool for large-scale hunting and can significantly reduce the time spent on manual analysis.

PowerShell Persistence Hunter

Repository: https://github.com/redcanaryco/PowerShell-Persistence-Hunter

PowerShell Persistence Hunter is another valuable tool in your DFIR arsenal. It is designed to detect PowerShell-based persistence mechanisms, a common technique used by adversaries. PowerShell is a powerful scripting language that can be abused to maintain persistence in a system. PowerShell Persistence Hunter scans for common PowerShell persistence techniques, such as scheduled jobs, event subscriptions, and profile modifications.

To install PowerShell Persistence Hunter, follow these steps:

“`
PS > git clone https://github.com/redcanaryco/PowerShell-Persistence-Hunter.git
PS > cd PowerShell-Persistence-Hunter
PS > .\PowerShell-Persistence-Hunter.ps1
“`

Once installed, you can run PowerShell Persistence Hunter with the following command:

“`
PS > .\PowerShell-Persistence-Hunter.ps1 -Scan
“`

PowerShell Persistence Hunter’s output is detailed and provides context for each detected persistence mechanism. It is an essential tool for detecting PowerShell-based persistence and can help you uncover hidden threats in your environment.

Conclusion

Persistence detection is a critical aspect of DFIR. By understanding and mastering the tools and techniques discussed in this article, you can significantly enhance your ability to detect and mitigate persistence mechanisms employed by adversaries. Remember, the key to effective persistence detection lies in a combination of comprehensive scanning, manual validation, and continuous monitoring.

FAQ

Q: What is the best way to detect persistence mechanisms in a Windows environment?
A: The best way to detect persistence mechanisms is to use a combination of tools such as PersistenceSniper, Trawler, and PowerShell Persistence Hunter. These tools can help you identify and analyze persistence mechanisms in your environment.

Q: How can I validate the findings from persistence detection tools?
A: Always validate the findings from persistence detection tools manually. A “no findings” result does not guarantee a clean system, and manual validation is essential to ensure accuracy.

Q: What are the common persistence techniques used by adversaries?
A: Common persistence techniques include scheduled tasks, services, Run keys, Winlogon, Startup folders, WMI persistent subscriptions, AppInit DLLs, service image paths, and PowerShell-based persistence mechanisms.

Q: How can I reduce the noise from benign services in my persistence detection results?
A: Tools like Trawler are designed to reduce noise by focusing only on items that look like adversary persistence. However, always validate any findings manually to ensure accuracy.

Q: What is the importance of continuous monitoring in persistence detection?
A: Continuous monitoring is crucial in persistence detection as it allows you to detect and respond to new persistence mechanisms that may emerge in your environment. Regular scanning and analysis can help you maintain a secure and resilient system.