infostealers

infostealers is a skill for Claude Code from Liberty91LTD/cti-skills. It costs 72 tokens per session (2,810 once invoked), scanned A, original, MIT.

A security research guide about infostealers, malware that secretly collects information such as saved passwords, browser session data, and cryptocurrency wallet details. It also covers the criminal marketplaces where stolen data is traded.

In plain words
What is it for?
Use it to investigate infostealer families, stolen-data marketplaces, and incidents involving exposed credentials or malware logs.
Why use it?
It helps explain how stolen credentials and browser data can lead to account takeovers, fraud, and wider network break-ins.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter. Also seen: positional $N argument.

Good fit Use it to investigate infostealer families, stolen-data marketplaces, and incidents involving exposed credentials or malware logs.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/liberty91ltd/cti-skills/infostealers
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 Liberty91LTD/cti-skills --skill infostealers
Clone the repo
git clone --depth 1 https://github.com/Liberty91LTD/cti-skills

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for infostealers

README.md
[![agentmods](https://agentmods.dev/badge/skills/liberty91ltd/cti-skills/infostealers/github.svg)](https://agentmods.dev/skills/liberty91ltd/cti-skills/infostealers)
Your own site
<a href="https://agentmods.dev/skills/liberty91ltd/cti-skills/infostealers"><img src="https://agentmods.dev/badge/skills/liberty91ltd/cti-skills/infostealers/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for infostealers

Your own site · 80×15
<a href="https://agentmods.dev/skills/liberty91ltd/cti-skills/infostealers"><img src="https://agentmods.dev/badge/skills/liberty91ltd/cti-skills/infostealers.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 72 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,810 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 $0.00072 $0.02810
Opus 5 $0.00036 $0.01405
Sonnet 5 $0.00014 $0.00562
Haiku 4.5 $0.00007 $0.00281

Measured 13d ago against content hash d5bb71f9d45a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

infostealers 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 13d ago.

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/infostealers/SKILL.md · 124 lines

How it starts

The opening of the file, as written. The whole thing — 124 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Infostealers

Executive Summary

Infostealer malware has become one of the most consequential threats in the cybercrime ecosystem, serving as a foundational enabler for ransomware, account takeover, corporate network intrusion, and financial fraud. These malware families operate under a Malware-as-a-Service (MaaS) model, with developers offering subscriptions ($100-$300/month) that include the malware builder, a management panel, and regular updates to evade detection. Upon execution, infostealers harvest browser-stored credentials, session cookies, cryptocurrency wallet data, autofill data, and system information, packaging the results into "logs" that are then sold on dedicated marketplaces or used directly by the operator.

The log marketplace ecosystem is substantial. Russian Market has emerged as the dominant platform for purchasing individual infostealer logs, following the law enforcement takedown of Genesis Market in April 2023 (Operation Cookie Monster). Genesis Market had been unique in selling persistent "bot" access that included browser fingerprints, enabling buyers to impersonate victims' browser sessions. Telegram channels also serve as major distribution points for both bulk and individual log sales. A single high-value corporate log — containing VPN credentials, SSO session cookies, or cloud service tokens — can sell for $10-$500, while bulk residential logs sell for as little as $1-$10 each.

The connection between infostealers and ransomware operations has tightened significantly. Initial Access Brokers (IABs) systematically harvest corporate VPN, RDP, and Citrix credentials from infostealer logs and resell this access to ransomware affiliates. Many ransomware incidents can be traced back to credentials originally stolen by infostealers months earlier. Distribution methods have evolved from traditional email spam to sophisticated SEO poisoning campaigns, malvertising through Google Ads, and trojanized software downloads, making infostealers a pervasive threat that affects both individual consumers and enterprises.

Read the full file on GitHub · 124 lines

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. 13d ago First seen · 124 lines · 72 tokens per session scan A d5bb71f9d45a

Subscribe to this mod's changes

infostealers is a skill published in the GitHub repository Liberty91LTD/cti-skills (18 stars, last pushed 1mo ago), licensed MIT. It adds 72 tokens to every session and 2,810 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 2026-08-30.