model-dos

A security check for AI model endpoints, which are services that receive prompts and return model-generated text. It looks for missing limits on prompt size, generated output, and request frequency.

In plain words
What is it for?
Use it in chatbot backends, model API handlers, and inference services. It helps review output-token caps, input-length limits, accumulated conversation context, and per-user or per-IP rate limits.
Why use it?
An attacker can send huge or repeated prompts, or keep adding chat history, to consume computing resources and increase costs. This can slow or block service for other users.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/thejefflarson/soundcheck/model-dos
Any agent
npx skills add thejefflarson/soundcheck --skill model-dos
Clone the repo
git clone --depth 1 https://github.com/thejefflarson/soundcheck

Made for: Claude Code, Codex.

Per session 67 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 837 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00067 $0.00837
Opus 5 $0.00034 $0.00418
Sonnet 5 $0.00013 $0.00167
Haiku 4.5 $0.00007 $0.00084

Measured 2d ago against content hash c3a5c2c54ba2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

model-dos 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 2d 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.

.claude/skills/model-dos/SKILL.md · 67 lines

How it starts

The opening of the file, as written. The whole thing — 67 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Model Denial of Service Security Check (OWASP LLM04:2025)

What this checks

Protects against resource exhaustion caused by unbounded prompts, missing token caps, or absent rate limiting. Attackers can submit enormous or recursive inputs that inflate inference costs, saturate GPU/CPU, and deny service to legitimate users.

Vulnerable patterns

  • LLM API calls with no max_tokens parameter — model generates until its internal limit
  • No input length validation before sending to the inference endpoint
  • Multi-turn chat that accumulates context indefinitely across turns
  • No per-user or per-IP rate limiting on the prompt endpoint

Fix immediately

Flag the vulnerable code and explain the risk. Then suggest a fix that establishes these properties:

  1. Every LLM call sets an explicit output cap — the provider's max-tokens parameter or its equivalent. Leaving it at the provider default lets a single request run for minutes and rack up dollars in tokens.
  2. Prompt input is length-capped at the handler boundary before it reaches the inference client. Measured in chars, bytes, or tokens — the exact unit does not matter as long as the cap runs before the upstream call.
  3. Conversation context is bounded. Either the handler is stateless single-turn, or accumulated history is trimmed to a fixed turn or token budget before every call. Unbounded history is an attacker's favorite amplifier.
  4. Per-identifier throttling (per user, per API key, per IP) runs on every LLM endpoint. In-process token bucket, framework middleware, or reverse-proxy rule — anything that survives alias and batch tricks and prevents one caller from pinning the endpoint.
  5. Every inference call has a deadline. SDK timeout, HTTP client timeout, or request-context cancellation — a hung upstream must not be able to indefinitely occupy a worker.

Translate each principle to the inference SDK, web framework, and rate-limiter of the audited file. Use the SDK's documented cap and timeout parameters — do not rely on global defaults.

Read the full file on GitHub · 67 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. 2d ago First seen · 67 lines · 67 tokens per session scan A c3a5c2c54ba2

Subscribe to this mod's changes

model-dos is a skill published in the GitHub repository thejefflarson/soundcheck (20 stars, last pushed 1mo ago), licensed MIT. It adds 67 tokens to every session and 837 once invoked, about $0.0003 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.

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