hunting-suspicious-powershell-execution

hunting-suspicious-powershell-execution is a skill for Claude Code, Codex from meltedinhex/analyst-ai-pack. It costs 79 tokens per session (800 once invoked), scanned A, original, Apache-2.0.

A security-hunting guide for examining PowerShell logs to find suspicious scripts, including encoded commands, downloads, attempts to bypass protection, and code run directly in memory. PowerShell is Windows' command and scripting environment.

In plain words
What is it for?
Use it to collect and reassemble script-block logs, score combinations of suspicious behavior, decode payloads, and create a triage queue.
Why use it?
It helps separate likely abuse from legitimate administration, which may use many of the same commands.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to collect and reassemble script-block logs, score combinations of suspicious behavior, decode payloads, and create a triage queue.

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Install with agentmods
npx agentmods add skills/meltedinhex/analyst-ai-pack/hunting-suspicious-powershell-execution
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add meltedinhex/analyst-ai-pack --skill hunting-suspicious-powershell-execution
Clone the repo
git clone --depth 1 https://github.com/meltedinhex/analyst-ai-pack

Made for: Claude Code, Codex.

Wrote this? Show the measurements

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README.md
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Your own site · 80×15
<a href="https://agentmods.dev/skills/meltedinhex/analyst-ai-pack/hunting-suspicious-powershell-execution"><img src="https://agentmods.dev/badge/skills/meltedinhex/analyst-ai-pack/hunting-suspicious-powershell-execution.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 79 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 800 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00079 $0.00800
Opus 5 $0.00039 $0.00400
Sonnet 5 $0.00016 $0.00160
Haiku 4.5 $0.00008 $0.00080

Measured 6d ago against content hash 6a9a6799d7ff, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

hunting-suspicious-powershell-execution scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/analyst.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/hunting-suspicious-powershell-execution/SKILL.md · 95 lines

How it starts

The opening of the file, as written. The whole thing — 95 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Hunting Suspicious PowerShell Execution

When to Use

  • You have PowerShell script-block (Event ID 4104) and/or module logging and want to hunt abuse.
  • You are testing a hypothesis that attackers use encoded commands, download cradles, or AMSI/logging bypasses.
  • You need to score and decode a large volume of PowerShell events into a triage queue.

Do not use simple keyword blocklists as the sole method — admins legitimately use many of the same cmdlets; score combinations and decode before judging.

Prerequisites

  • Script-block logging enabled (Event ID 4104) and exported to a queryable store.
  • A baseline of normal administrative PowerShell for your environment.

Workflow

Step 1: Collect script-block events

Pull EID 4104 script-block text (and EID 4103 module logging) over the hunt window. Reassemble multi-part script blocks before analysis.

Step 2: Score suspicious constructs

Weight combinations rather than single keywords: -EncodedCommand, IEX/Invoke-Expression with Net.WebClient/Invoke-WebRequest, FromBase64String, -w hidden -nop, AMSI strings, and [Ref].Assembly reflection.

python scripts/analyst.py score events.json

Step 3: Decode payloads

Base64-decode -EncodedCommand (UTF-16LE) and recover layered encodings to read the real intent (download URLs, in-memory loaders).

Step 4: Baseline and pivot

Compare against normal admin activity; for survivors, pull the parent process, user, host, and network connections to confirm.

Step 5: Confirm and operationalize

Validate true positives, escalate to IR, and convert the scoring logic into a detection rule.

Validation

  • High-score events decode to coherent malicious intent, not benign admin scripts.
  • Multi-part script blocks are reassembled before scoring (no truncated false negatives).
  • Confirmed cases tie to a parent process and user consistent with intrusion.

Pitfalls

  • Flagging single keywords (IEX alone) and drowning in admin noise.
  • Forgetting -EncodedCommand is UTF-16LE, producing garbled decodes.
  • Ignoring AMSI/logging-bypass attempts that precede the real payload.

Read the full file on GitHub · 95 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 6d ago First seen · 95 lines · 79 tokens per session scan A 6a9a6799d7ff

Subscribe to this mod's changes

hunting-suspicious-powershell-execution is a skill published in the GitHub repository meltedinhex/analyst-ai-pack (22 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 79 tokens to every session and 800 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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