A recent research disclosure from security researcher TwoSevenOneT describes EDR-Redir V2, an evolution of a filesystem redirection technique that aims to blind Endpoint Detection and Response (EDR) products by manipulating filesystem namespaces. The finding is notable not because it’s a polished exploit, but because it highlights a class of weaknesses in how many EDRs protect their on-disk assets — and it shows why defenders should broaden their monitoring and integrity strategies.
Quick summary (TL;DR)
- What it is: A technique leveraging Windows bind-link (namespace redirection) behavior to create directory redirection loops that can obscure an EDR’s view of its own files.
- Why it matters: Parent-level redirections can bypass folder-level protections many vendors rely on, potentially enabling code-injection or tampering attempts to go undetected.
- What defenders should do: Monitor namespace/bind operations, implement integrity checks on EDR paths and critical binaries, and work with vendors to harden parent-directory protections without breaking legitimate software.
What the research shows (high level)
TwoSevenOneT’s research demonstrates that manipulating filesystem namespace bindings can cause security software to access an attacker-controlled mirror of its files, rather than the originals. The research stresses a shift from direct folder redirections to parent-level manipulation, which can be harder to lock down: many protections focus on locking specific subfolders of an EDR installation but do not comprehensively guard parent directories because doing so risks breaking legitimate installers and applications.
Importantly, this write-up does not repeat any exploit commands or procedural details. The goal here is to communicate the risk to defenders, not to enable misuse.
Why parent-level redirections are a unique concern
- Granularity mismatch: Vendors often protect known EDR subfolders; parent folders are frequently left writable to preserve installation and upgrade workflows.
- Namespace complexity: Modern Windows namespace features can redirect file system views without obvious changes to file contents, complicating traditional integrity checks.
- Low-noise user-mode effects: Because some namespace redirections operate in user mode, they can produce fewer kernel events and less obvious telemetry, making detection harder.
Potential impacts
- Visibility loss: EDRs may read and act on attacker-controlled files, missing real tampering.
- Tamper and injection opportunities: If an EDR is tricked into loading files from a redirected location, attackers could attempt DLL hijacking or other file-based manipulations.
- Enterprise risk: In large environments, small gaps in parent-directory protections could affect many endpoints at once.
Defensive strategies (non-actionable, practical guidance)
Below are safe, high-level defensive actions organizations and vendors should consider:
For security operations teams
- Monitor namespace operations and unusual mount/bind activity: Instrument logging systems to surface uncommon namespace redirections or unusual directory mapping events affecting critical directories.
- File integrity monitoring (FIM): Enforce integrity checks not just on protected subfolders and binaries but on the full path chain from root→parent→child for critical security components.
- Audit parent-directory writes: Put alerting thresholds on write or rename activity targeting the parent folders of security products, especially outside normal installer/update windows.
- Endpoint telemetry correlation: Correlate filesystem namespace changes with process creation, driver loads, service restarts, and network activity to detect suspicious chains of events.
- Least privilege and hardening: Ensure administrative policies minimize unnecessary write access to critical parent directories without breaking legitimate software workflows.
For EDR vendors
- Expand threat model: Consider parent-directory manipulation as an attack vector and evaluate protections that do not overly restrict legitimate installers.
- Harden path resolution: Implement path resolution and verification that detects when the logical view of a directory differs from its expected physical contents.
- Integrity anchors: Use cryptographic integrity checks and trusted storage for core components, and validate the provenance of loaded modules at runtime.
- Telemetry and alerting: Surface suspicious namespace or bind operations in management consoles with meaningful indicators for SOC analysts.
Monitoring signals to prioritize
(High-level examples — not detection rules or code.)
- Sudden or persistent write activity in parent directories of security products outside of known maintenance windows.
- Unexpected changes in the resolved path of a security product’s runtime files (when compared against a trusted inventory).
- Correlated events where process loads or service restarts follow namespace/redirect operations.
Why this matters for enterprise security posture
EDR solutions are a last line of defense for many organizations. Research like this doesn’t necessarily show a simple, widely-exploited worm — instead, it highlights a category of filesystem manipulations that could erode EDR effectiveness if left unmonitored. Proactive detection, stronger integrity checking, and vendor collaboration are the right responses.
Responsible disclosure & community takeaways
Researchers publishing these findings play a valuable role in improving security. Defenders should treat such reports as a call to action: validate your protections, update monitoring, and collaborate with vendors to make parent-level protections practical and robust.
Conclusion
EDR-Redir V2’s core insight is a reminder that attackers — and researchers — continue to explore new ways to manipulate the operating environment. The takeaway for defenders is clear: broaden your visibility beyond per-product subfolders, monitor namespace and path-resolution anomalies, and adopt stronger integrity and telemetry collection for critical security paths.
