Detecting Suspicious Powershell Execution

What it does

When your agent uses it

• Proactively threat hunting
• Triaging EDR/SIEM alerts
• Scoping an incident involving malicious PowerShell activity

Example prompts

• “/detecting-suspicious-powershell-execution”

Requirements

• Python 3

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

1. 1Formulate Hypothesis: Define a testable hypothesis based on threat intelligence or ATT&CK gap analysis.
2. 2Identify Data Sources: Determine which logs and telemetry are needed to validate or refute the hypothesis.
3. 3Execute Queries: Run detection queries against SIEM and EDR platforms to collect relevant events.
4. 4Analyze Results: Examine query results for anomalies, correlating across multiple data sources.
5. 5Validate Findings: Distinguish true positives from false positives through contextual analysis.
6. 6Correlate Activity: Link findings to broader attack chains and threat actor TTPs.
7. 7Document and Report: Record findings, update detection rules, and recommend response actions.

What it can do on your machine

Read from SKILL.md and the folder at commit 54a7988. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships 2 files in scripts/ (Python), which the agent can run.

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Detecting Suspicious Powershell Execution loads about 923 tokens when it runs, and up to ~2.7k if it reads all its reference files. Until then it costs about 107 tokens; SKILL.md has 304 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~107

When it runs · the whole SKILL.md, loaded when a task matches

~923

With references · SKILL.md plus every file in references/, read only if the agent opens them

~2.7k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from mukul975/Anthropic-Cybersecurity-Skills at commit 54a7988, republished under its Apache-2.0 licence (© mukul975). 304 words, ~923 tokens.

name

detecting-suspicious-powershell-execution

description

Hunt for suspicious PowerShell execution (T1059.001) such as encoded commands, download cradles, AMSI bypass, and constrained language mode evasion using EDR telemetry (CrowdStrike, Microsoft Defender for Endpoint), Sysmon, and SIEM queries (Splunk, Elastic). Use when proactively threat hunting, triaging EDR/SIEM alerts, or scoping an incident involving malicious PowerShell activity.

domain

cybersecurity

subdomain

threat-hunting

tags

threat-hunting, mitre-attack, powershell, execution, t1059, amsi, proactive-detection

version

1.0

author

mahipal

license

Apache-2.0

d3fend_techniques

Executable Denylisting, Execution Isolation, File Metadata Consistency Validation, Content Format Conversion, File Content Analysis

nist_csf

DE.CM-01, DE.AE-02, DE.AE-07, ID.RA-05

mitre_attack

T1059.001, T1027.010, T1620, T1105

Hunt ID: TH-DETECT-[DATE]-[SEQ]
Technique: T1059.001
Host: [Hostname]
User: [Account context]
Evidence: [Log entries, process trees, network data]
Risk Level: [Critical/High/Medium/Low]
Confidence: [High/Medium/Low]
Recommended Action: [Containment, investigation, monitoring]

© mukul975, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 7 other files (scripts, references, assets) in skills/detecting-suspicious-powershell-execution of mukul975/Anthropic-Cybersecurity-Skills.

• SKILL.md
• LICENSE
• assets/template.md
• references/api-reference.md
• references/standards.md
• references/workflows.md
• scripts/agent.py
• scripts/process.py

Open the folder on GitHubat commit 54a7988