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Hunting fileless and in memory threats

Skill meltedinhex/analyst-ai-pack/skills/hunting-fileless-and-in-memory-threats

An open agent-skills library for malware analysis, reverse engineering, and threat hunting - 118 curated, runnable skills mapped to MITRE ATT&CK, D3FEND, and CAR.

Install
npx -y skills add meltedinhex/analyst-ai-pack --skill hunting-fileless-and-in-memory-threats

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  • 19 stars19 stars. Stars are a popularity signal and not a quality one, but at this level it is likely that nobody has read this closely except its author, and you would be relying on your own review.

What its author says it does

Copied from the file, not written here

Hunts for fileless and in-memory threats by correlating PowerShell script-block logs, encoded-command usage, in-memory loading patterns, and registry-resident payloads from Windows telemetry. Activates for requests to hunt fileless malware, detect in-memory execution, or find registry-resident and reflective-loading activity.

The file declares its own license as Apache-2.0. That is the author’s claim about this one file, and it is not the same thing as the license GitHub reports for the repository, which is listed with the other numbers below.

SKILL.md

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Hunting Fileless and In-Memory Threats

When to Use

  • You have PowerShell script-block logs (4104), process telemetry, and registry-write events and want to detect fileless execution that leaves little on disk.
  • You are hunting reflective loading, in-memory .NET execution, and registry-resident payloads.

Do not use this to alert on all PowerShell use — hunt the in-memory loading and encoded-payload patterns specifically.

Prerequisites

  • 4104 script-block logs and/or process and registry telemetry (CSV/JSON).

Workflow

Step 1: Hunt in-memory loading patterns

python scripts/analyst.py hunt events.csv

Flags [Reflection.Assembly]::Load, VirtualAlloc/WriteProcessMemory via PowerShell, Invoke-Expression of decoded blobs, DownloadString+IEX, and large base64 in script blocks.

Step 2: Detect registry-resident payloads

Surface writes of large encoded blobs to HKCU\Software\... Run-adjacent or custom keys (fileless storage).

Step 3: Confirm

Correlate script-block content with the parent process and subsequent network/child activity.

Step 4: Operationalize

Write detections for reflective loading and base64-heavy script blocks.

Validation

  • Flags are based on in-memory loading/encoded-payload patterns, not PowerShell presence.
  • Registry-resident payload detection keys on large encoded values.
  • Findings map to ATT&CK T1620/T1059.001/T1112.

Pitfalls

  • Legitimate admin scripts using Invoke-Expression — corroborate with content/parent.
  • Obfuscated script blocks splitting indicators across logs.
  • Constrained Language Mode evasions changing the observable API surface.

References

Keep looking

Skills are one crate of 328,083. Ordering is by how many stacks a row turns up in, so the top of any crate is what has actually been picked rather than what has the most stars.