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Introduction:
Modern EDR solutions like CrowdStrike Falcon employ user‑land hooks, event tracing, and memory scanning to detect credential dumping techniques (T1003). However, as Hernan Rodriguez demonstrated, an updated version of `Invoke‑M1m1fud` can bypass Falcon’s in‑memory detection when dumping registry hives. But evasion is only half the battle – the Purple Team mindset shifts from “how to bypass” to “how to detect the bypass.” Using Splunk, regex correlation, and indexed sourcetypes, defenders can manually hunt for OS credential dumping even when traditional alerts fail.
Learning Objectives:
- Understand how `Invoke‑M1m1fud` bypasses EDR memory detection for registry‑based credential dumping.
- Build Splunk correlation searches to detect T1003 via registry access events, process ancestry, and timing anomalies.
- Apply Purple Team tactics – blending Red Team evasion with Blue Team detection engineering on Windows endpoints.
You Should Know:
- Weaponizing Invoke‑M1m1fud: Memory‑Only Registry Dumping to Evade Falcon EDR
`Invoke‑M1m1fud` is a PowerShell script designed to obfuscate and execute reflective injection of Mimikatz or similar tools. Hernan’s updated version focuses on dumping registry hives (SAM, SECURITY, SYSTEM) directly from memory without writing to disk, bypassing Falcon’s on‑write scanning. Below is a simplified PowerShell snippet illustrating the core concept – reading registry hive data into memory and extracting hashes using .NET classes.
Memory-only registry hive read (Windows) $hivePath = "C:\Windows\System32\config\SAM" $bytes = [System.IO.File]::ReadAllBytes($hivePath) Decrypt and parse using offline Mimikatz logic (simplified) Add-Type -Path "C:\Tools\RawRegistryHive.dll" $hashes = Extract‑Hashes -HiveBytes $bytes
Step‑by‑step guide to simulate and detect this technique:
- Simulation (Red Team) – On a test Windows 10/Server, run the memory‑only hive reader. Use ProcMon to verify no file write occurs to
SAM. - Bypass check – Execute with CrowdStrike Falcon sensor active. If no alert triggers, the evasion works.
- Detection (Purple Team) – Enable advanced audit policies:
auditpol /set /subcategory:"Registry" /success:enable. Forward Event ID 4657 (registry value changes) and 4663 (registry handle access) to Splunk.
4. Splunk search for anomalous hive access –
`index=windows sourcetype=WinEventLog:Security (EventCode=4657 OR EventCode=4663) ObjectName=”\\SAM” OR ObjectName=”\\SECURITY”`
Add `| stats count by ProcessName, SubjectUserName, ComputerName` to identify processes not typically accessing these hives (e.g., `powershell.exe` from non‑admin user).
- Splunk Correlation Hunting: Regex, Sourcetype Mapping, and Indexing for T1003
Hernan emphasized regex matching, event correlation, and sourcetype enrichment. To hunt credential dumping, you must link multiple data sources: Windows Security logs, Sysmon (Event ID 10 – ProcessAccess, Event ID 1 – ProcessCreation), and EDR telemetry. Below is a step‑by‑step to build a T1003 detection in Splunk.
Step‑by‑step guide:
- Ingest Sysmon – Install Sysmon with a configuration that logs `ProcessAccess` (Event ID 10) for `lsass.exe` and registry hive reads. Forward to Splunk with sourcetype
XmlWinEventLog. - Extract key fields using regex – In Splunk’s props.conf:
`EXTRACT-target = TargetImage=\”(?[^\”]+)\”`
`EXTRACT-source = SourceImage=\”(?[^\”]+)\”`
`EXTRACT-call = CallTrace=\”(?[^\”]+)\”`
3. Correlation search for LSASS access –
`index=windows sourcetype=”XmlWinEventLog” EventID=10 TargetImage=”\\lsass.exe” SourceImage=”\\powershell.exe” OR SourceImage=”\\wmic.exe”`
`| stats count by SourceImage, TargetImage, ComputerName, _time`
`| where count > 3` (unusually high handles).
4. Registry dumping correlation –
`index=windows (EventCode=4657 OR sourcetype=”WinEventLog:Security”) “\\SAM” OR “\\SECURITY”`
`| eval ProcessKey = ProcessName . ComputerName`
`| transaction ProcessKey maxspan=5m` – groups events from the same process within 5 minutes.
5. Alert threshold – Use `| where eventcount > 10` to trigger a high‑fidelity alert. Add a lookup to exclude known backup software.
- Blue Team Tooling: Configuring Suricata and Snort for Web‑Service Attack Detection
Hernan mentioned customizing IDS/IPS templates for web attacks during his Banco Pichincha days. While T1003 is endpoint‑focused, credential dumping often follows initial web exploitation (e.g., SQLi to shell). Below are Suricata rules to detect credential harvesting from web apps.
Step‑by‑step guide:
- Install Suricata on a Linux sensor (Ubuntu 22.04):
`sudo add-apt-repository ppa:oisf/suricata-stable && sudo apt update && sudo apt install suricata`
2. Enable HTTP logging in `/etc/suricata/suricata.yaml`:
`http-log: enabled: yes, filename: http.log`
- Custom rule to detect /etc/passwd or SAM download –
`alert http any any -> any any (msg:”Possible credential file access”; flow:established,to_server; content:”/etc/passwd”; http_uri; sid:1000001; rev:1;)`
For Windows web servers: `content:”/windows/repair/sam”; http_uri;`
- Test rule – Use `curl http://target/vulnerable.jsp?file=../../windows/repair/sam`. Suricata should log alert.
- Forward to Splunk – Install Splunk Universal Forwarder on the Suricata host, monitor
/var/log/suricata/fast.log. Create a sourcetypesuricata:alerts. Then hunt:
`index=security sourcetype=suricata:alerts “credential file access”`
- Linux Commands for Purple Team: Simulating and Detecting Credential Dumping on Linux (T1003.008)
Though the post focuses on Windows, Purple Teams need cross‑platform coverage. Linux credential dumping often targets /etc/shadow. Below are commands to simulate and detect.
Simulate (Red Team):
Dump shadow with low-level read (bypassing some EDR) sudo dd if=/etc/shadow bs=1 2>/dev/null | strings Or using unshadow sudo unshadow /etc/passwd /etc/shadow > /tmp/crack.txt
Detection (Blue Team) on Linux with auditd:
Install auditd sudo apt install auditd -y Add rule to monitor /etc/shadow reads sudo auditctl -w /etc/shadow -p r -k T1003_shadow_dump Search logs sudo ausearch -k T1003_shadow_dump
Splunk integration – Forward `/var/log/audit/audit.log` to Splunk, sourcetype linux_audit. Search:
`index=linux sourcetype=linux_audit “key=T1003_shadow_dump” | table _time, uid, exe, auid`
5. Purple Team Workflow: From Offensive Script to Defensive Correlation
Hernan’s transition from Red to Purple highlights a key workflow: take a known offensive tool (e.g., Invoke-M1m1fud), run it in a lab with full logging, then build detection queries based on the forensic artifacts left behind – even if the EDR missed it.
Step‑by‑step Purple Team exercise:
- Setup lab – Two VMs: Windows 10 (attacker, with Falcon EDR in test mode) and Windows Server 2019 (target with Splunk Universal Forwarder + Sysmon).
- Execute attack – On the attacker VM, run Hernan’s updated `Invoke-M1m1fud` to dump `SAM` from target (using PSRemoting or WinRM).
- Collect all logs – In Splunk, index Windows Security, Sysmon, PowerShell Operational logs (Event ID 4104 – script block logging).
- Identify blind spots – Search for `index=windows sourcetype=WinEventLog:PowerShellOperational` after the attack. If Falcon suppressed alerts, but PowerShell logs show `Invoke-M1m1fud` execution, that’s a detection gap.
5. Build custom correlation –
`index=windows (EventCode=4104 Message=”Invoke-M1m1fud”) OR (EventCode=10 TargetImage=”\\lsass.exe”)`
`| stats min(_time) as first_seen, max(_time) as last_seen by ComputerName`
`| eval detection = if(last_seen – first_seen < 300, "CREDENTIAL_DUMP_LIKELY", "NORMAL")`
6. Create Splunk alert – Schedule the above search every 5 minutes, trigger when detection="CREDENTIAL_DUMP_LIKELY".
What Undercode Say:
- Key Takeaway 1: Purple Team success depends on merging offensive creativity (e.g., memory‑only registry dumping) with defensive patience – building regex correlations and manual hunting queries against indexed logs, not just EDR dashboards.
- Key Takeaway 2: Credential dumping (T1003) detection requires telemetry from multiple sources (Sysmon ProcessAccess, registry audit events, PowerShell script blocks) and time‑based correlation, because no single event is malicious in isolation.
Analysis (10 lines):
Hernan’s post underscores a critical shift in modern cybersecurity: attackers will always find new ways to bypass EDR, but defenders who adopt a Purple Team mindset can still detect the residual artifacts of those attacks – even when no alert fires. By using Splunk to manually hunt for patterns like registry hive access from unexpected processes or multiple LSASS handle requests, the defender moves beyond “alert waiting” to proactive threat hunting. The mention of `Invoke-M1m1fud` evolving to evade Falcon in memory is a call to action for Blue Teams: update your detection logic as evasion techniques advance. Arturo Simich’s mentorship at Banco Pichincha shows that embedding offensive specialists inside defensive operations (24×7) yields the deepest detection expertise. Finally, Hernan’s gratitude to his peers highlights that knowledge sharing – especially around custom regex, sourcetype mapping, and index correlation – is the bedrock of effective Purple Team collaboration. Without that, even the most advanced EDR remains blind to the human‑driven, low‑and‑slow credential dump.
Prediction:
As EDR vendors integrate more kernel‑level callbacks and AI‑based behavioral analysis, memory‑only attacks like `Invoke-M1m1fud` will face diminishing returns. However, Purple Teams will pivot to hunting behavioral sequences that precede credential dumping – anomalous registry handle duplication, unusual parent‑child process relationships (e.g., `powershell.exe` launching `reg.exe` with save), or cross‑index correlation between network logs (e.g., RDP brute force) and sudden registry hive reads. Within 18 months, we expect Splunk and similar SIEMs to offer native, MITRE‑aligned “Purple Team playbooks” that automatically generate detection rules from offensive tool signatures, shrinking the time between weaponization and detection from weeks to hours. The ultimate winner will not be the tool that evades best, but the team that correlates fastest.
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Reported By: Hernanrodriguez – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
