CyberExcellence Security
@cyberexCompletionist
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Identifies Node.js processes that spawn potentially suspicious child processes, including operating system shells, command interpreters, scripting runtimes, and download utilities. This behaviour may indicate exploitation of a Node.js application resulting in arbitrary command execution, followed by payload retrieval or additional post-exploitation activity.
The detection targets these behaviours:
- Attempts to take ownership of or replace explorer.exe and gpedit.msc.
- Changes to Microsoft Edge's Image File Execution Options (IFEO) debugger.
- Changes to HTTP, HTTPS, HTML, and Microsoft Edge protocol handlers.
- Disabling Explorer's Run command and changing keyboard scancode mappings.
- Creation of temporary VBScript files used for relaunching, elevation prompts, or deceptive messages
- Attempts to take ownership of or replace explorer.exe and gpedit.msc.
- Changes to Microsoft Edge's Image File Execution Options (IFEO) debugger.
- Changes to HTTP, HTTPS, HTML, and Microsoft Edge protocol handlers.
- Disabling Explorer's Run command and changing keyboard scancode mappings.
- Creation of temporary VBScript files used for relaunching, elevation prompts, or deceptive messages
The KQL rule detects a ClickFix-style technique in which script hosts reference files disguised with an f_* naming pattern in browser profile cache directories. The key behavioural indicators are:
- Script hosts such as wscript.exe, cscript.exe, and mshta.exe referencing browser cache paths.
- Suspicious parent processes, including Explorer, command shells, and script hosts.
- Creation, modification, or renaming of t.vbs under the user's Temp directory by Windows Script Host.
- Script hosts such as wscript.exe, cscript.exe, and mshta.exe referencing browser cache paths.
- Suspicious parent processes, including Explorer, command shells, and script hosts.
- Creation, modification, or renaming of t.vbs under the user's Temp directory by Windows Script Host.
MSI-backed loader execution chain
Cortex XDR
This query uses the process ID of each child to match the parent process's PID, then reconstructs the chain back to explorer.exe. It also checks for the encoded PowerShell, silent MSI installation, and embedded MSI execution behaviours described in the source article.
Important caveats
- Causality scope: This finds matching process events within a shared causality ID; it does not establish that each process directly launched the next.
- Explorer root: The root process may not share the same causality ID in every telemetry scenario. If this join removes otherwise valid results, investigate the root separately.
- Strict matching: Requiring every stage will miss partial chains and variants with different command-line arguments. Consider separate alerts for the encoded PowerShell and silent MSI behaviours.
- Validation: Confirm the field names, join syntax, and causality-ID population against your tenant before deploying this as a production detection.
Important caveats
- Causality scope: This finds matching process events within a shared causality ID; it does not establish that each process directly launched the next.
- Explorer root: The root process may not share the same causality ID in every telemetry scenario. If this join removes otherwise valid results, investigate the root separately.
- Strict matching: Requiring every stage will miss partial chains and variants with different command-line arguments. Consider separate alerts for the encoded PowerShell and silent MSI behaviours.
- Validation: Confirm the field names, join syntax, and causality-ID population against your tenant before deploying this as a production detection.