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Agent skill

Hunting Credential Stuffing Attacks

by mukul975 in mukul975/Anthropic-Cybersecurity-Skills

Detects credential stuffing attacks by analyzing authentication logs for login velocity anomalies, ASN diversity, password spray patterns, and geographic distribution of failed logins.

Apache-2.0Auto-check passedSecurity

Install Hunting Credential Stuffing Attacks

skills CLI
$ npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill hunting-credential-stuffing-attacks -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install mukul975/Anthropic-Cybersecurity-Skills hunting-credential-stuffing-attacks --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/mukul975/Anthropic-Cybersecurity-Skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/hunting-credential-stuffing-attacks .claude/skills/hunting-credential-stuffing-attacks && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
hunting-credential-stuffing-attacks
GitHub stars
34k
Token cost
~732 tokens
SKILL.md length
138 words
Files
4 (incl. scripts, references)
Skills in repo
644
Repo updated
First seen
Licence
Apache-2.0

At a glance

Detects credential stuffing attacks by analyzing authentication logs for login velocity anomalies, ASN diversity, password spray patterns, and geographic distribution of failed logins.

  • Works in 5 steps: High unique source IPs per failed username → Low success rate across many accounts (<… → ASN concentration from cloud/proxy… → …
  • Investigating account takeover campaigns
  • SKILL.md covers When to Use, Prerequisites, Instructions and Examples
  • Runs Python scripts from its folder

What it does

Hunting Credential Stuffing Attacks is an agent skill from mukul975/Anthropic-Cybersecurity-Skills. Detects credential stuffing attacks by analyzing authentication logs for login velocity anomalies, ASN diversity, password spray patterns, and geographic distribution of failed logins. Uses statistical analysis on Splunk or raw log data. Use when investigating account takeover campaigns or building detection rules for auth abuse.

Its SKILL.md is about 730 tokens, which your agent loads only when the skill is triggered. The skill folder holds 5 other files, including scripts and reference files (for example `references/api-reference.md` and `scripts/agent.py`).

It sits in Security, covering Statistics. It works with Splunk. The repository describes itself as: 817 structured cybersecurity skills for AI agents · Mapped to 6 frameworks: MITRE ATT&CK, NIST CSF 2.0, MITRE ATLAS, D3FEND, NIST AI RMF & MITRE F3 (Fight Fraud) · agentskills.io…. The licence is Apache-2.0.

When your agent uses it

  • Investigating account takeover campaigns
  • Building detection rules for auth abuse

Example prompts

  • “Use the hunting-credential-stuffing-attacks skill to detect credential stuffing attacks by analyzing authentication logs for login velocity…”
  • “/hunting-credential-stuffing-attacks”

Requirements

  • Python 3

Workflow steps

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

  1. High unique source IPs per failed username
  2. Low success rate across many accounts (< 1%)
  3. ASN concentration from cloud/proxy providers
  4. Geographic impossibility (same account, distant locations)
  5. User-agent uniformity across distributed IPs

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 1 file 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

Hunting Credential Stuffing Attacks loads about 732 tokens when it runs, and up to ~1.1k if it reads all its reference files. Until then it costs about 92 tokens; SKILL.md has 138 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~92
When it runs · the whole SKILL.md, loaded when a task matches
~732
With references · SKILL.md plus every file in references/, read only if the agent opens them
~1.1k

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

Auto-check passed

The automated check found no risky patterns in SKILL.md.

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). 138 words, ~732 tokens.

Download SKILL.mdSave it as .claude/skills/hunting-credential-stuffing-attacks/SKILL.md (or your agent's skills folder). This skill also uses 3 other files; get the full folder from GitHub.
name
hunting-credential-stuffing-attacks
description
Detects credential stuffing attacks by analyzing authentication logs for login velocity anomalies, ASN diversity, password spray patterns, and geographic distribution of failed logins. Uses statistical analysis on Splunk or raw log data. Use when investigating account takeover campaigns or building detection rules for auth abuse.
domain
cybersecurity
subdomain
security-operations
tags
credential-stuffing, authentication-logs, login-anomaly, asn-analysis, threat-hunting, account-takeover
version
1.0
author
mahipal
license
Apache-2.0
nist_csf
DE.CM-01, RS.MA-01, GV.OV-01, DE.AE-02
mitre_attack
T1078, T1190, T1059, T1003, T1110
mitre_f3.version
1.1
mitre_f3.tactics
initial-access, positioning

Hunting Credential Stuffing Attacks

When to Use

  • When investigating security incidents that require hunting credential stuffing attacks
  • When building detection rules or threat hunting queries for this domain
  • When SOC analysts need structured procedures for this analysis type
  • When validating security monitoring coverage for related attack techniques

Prerequisites

  • Familiarity with security operations concepts and tools
  • Access to a test or lab environment for safe execution
  • Python 3.8+ with required dependencies installed
  • Appropriate authorization for any testing activities

Instructions

Analyze authentication logs to detect credential stuffing by identifying patterns of distributed login failures, high IP diversity, and suspicious ASN distribution.

python
import pandas as pd
from collections import Counter

# Load auth logs
df = pd.read_csv("auth_logs.csv", parse_dates=["timestamp"])

# Credential stuffing indicator: many IPs trying few accounts
ip_per_account = df[df["status"] == "failed"].groupby("username")["source_ip"].nunique()
accounts_under_attack = ip_per_account[ip_per_account > 50]

Key detection indicators:

  1. High unique source IPs per failed username
  2. Low success rate across many accounts (< 1%)
  3. ASN concentration from cloud/proxy providers
  4. Geographic impossibility (same account, distant locations)
  5. User-agent uniformity across distributed IPs

Examples

python
# Password spray: one password tried across many accounts
spray = df[df["status"] == "failed"].groupby(["source_ip", "password_hash"]).agg(
    accounts=("username", "nunique")).reset_index()
sprays = spray[spray["accounts"] > 10]

© 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 3 other files (scripts, references) in skills/hunting-credential-stuffing-attacks of mukul975/Anthropic-Cybersecurity-Skills.

  • SKILL.md
  • LICENSE
  • references/api-reference.md
  • scripts/agent.py

Open the folder on GitHubat commit 54a7988

Compare with similar skills

Hunting Credential Stuffing Attacks next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Hunting Credential Stuffing Attacks compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Hunting Credential Stuffing Attacks this skillmukul975/Anthropic-Cybersecurity-Skills34k—~732Automated safety check: PassApache-2.0
Fla Ascend Performancefla-org/flash-linear-attention5.8k—~6.3kAutomated safety check: PassMIT
Constant Time Testingtrailofbits/skills7.4k—~5.2kAutomated safety check: PassCC-BY-SA-4.0
Detection SigmaAgentSecOps/SecOpsAgentKit2201 repos~4kAutomated safety check: PassCustom licence
Siem Detectionbriiirussell/cybersecurity-skills413—~2.6kAutomated safety check: NotesMIT
Doca ArgusNVIDIA/skills3.5k—~4.8kAutomated safety check: PassApache-2.0

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Works with

Categories

Questions about Hunting Credential Stuffing Attacks

What does Hunting Credential Stuffing Attacks do?

Detects credential stuffing attacks by analyzing authentication logs for login velocity anomalies, ASN diversity, password spray patterns, and geographic distribution of failed logins. Hunting Credential Stuffing Attacks is an agent skill from mukul975/Anthropic-Cybersecurity-Skills. Detects credential stuffing attacks by analyzing authentication logs for login velocity anomalies, ASN diversity, password spray patterns, and geographic distribution of failed logins.

When should I use Hunting Credential Stuffing Attacks?

Hunting Credential Stuffing Attacks fits situations like: investigating account takeover campaigns; building detection rules for auth abuse.

How do I install Hunting Credential Stuffing Attacks in Claude Code?

Run `npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill hunting-credential-stuffing-attacks -a claude-code`. Or copy the skill folder (skills/hunting-credential-stuffing-attacks in mukul975/Anthropic-Cybersecurity-Skills) into .claude/skills/hunting-credential-stuffing-attacks in your project. Claude Code loads it when a task matches its description.

How do I install Hunting Credential Stuffing Attacks in Codex?

Run `npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill hunting-credential-stuffing-attacks -a codex`. Or copy the skill folder (skills/hunting-credential-stuffing-attacks in mukul975/Anthropic-Cybersecurity-Skills) into .agents/skills/hunting-credential-stuffing-attacks in your project. Codex loads it when a task matches its description.

Can I use Hunting Credential Stuffing Attacks in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill hunting-credential-stuffing-attacks -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/hunting-credential-stuffing-attacks, .gemini/skills/hunting-credential-stuffing-attacks, .github/skills/hunting-credential-stuffing-attacks and .opencode/skills/hunting-credential-stuffing-attacks in your project.

What does Hunting Credential Stuffing Attacks need to run?

Going by SKILL.md and its folder, Hunting Credential Stuffing Attacks needs Python for the scripts in its folder. Our summary lists: Python 3.

Does Hunting Credential Stuffing Attacks access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Hunting Credential Stuffing Attacks safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Hunting Credential Stuffing Attacks use?

Hunting Credential Stuffing Attacks is published under the Apache-2.0 licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Hunting Credential Stuffing Attacks use?

About 732 tokens (SKILL.md is roughly 2.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 370 tokens, read only when the agent opens those files.

What are the alternatives to Hunting Credential Stuffing Attacks?

Skills that share tags, products or a category with Hunting Credential Stuffing Attacks: Fla Ascend Performance (fla-org/flash-linear-attention, 5.8k stars), Constant Time Testing (trailofbits/skills, 7.4k stars), Detection Sigma (AgentSecOps/SecOpsAgentKit, 220 stars) and Siem Detection (briiirussell/cybersecurity-skills, 413 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Hunting Credential Stuffing Attacks?

mukul975 (a GitHub user) maintains it in mukul975/Anthropic-Cybersecurity-Skills, which has 33,993 GitHub stars. The repository holds 644 skills in this directory. The repository was last updated on August 31, 2026.

Source: mukul975/Anthropic-Cybersecurity-Skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.