detecting-sandbox-evasion-behavior

detecting-sandbox-evasion-behavior is a skill for Claude Code, Codex from meltedinhex/analyst-ai-pack. It costs 79 tokens per session (689 once invoked), scanned A, original, Apache-2.0.

A static-analysis guide for finding signs that malware tries to detect or avoid virtual machines, sandboxes, or debuggers. A sandbox is a restricted environment used to observe suspicious software safely.

In plain words
What is it for?
Use it to scan strings, imported functions, and API traces for virtual-machine checks, anti-debugging, timing delays, and environment fingerprinting.
Why use it?
It helps explain why a sample may behave differently during analysis and highlights evasion as a warning sign. It does not prove that a sample is safe when no indicators are found.

Skill for Claude CodeCodex

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

Good fit Use it to scan strings, imported functions, and API traces for virtual-machine checks, anti-debugging, timing delays, and environment fingerprinting.

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Install with agentmods
npx agentmods add skills/meltedinhex/analyst-ai-pack/detecting-sandbox-evasion-behavior
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 detecting-sandbox-evasion-behavior
Clone the repo
git clone --depth 1 https://github.com/meltedinhex/analyst-ai-pack

Made for: Claude Code, Codex.

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 detecting-sandbox-evasion-behavior

README.md
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agentmods 80×15 button for detecting-sandbox-evasion-behavior

Your own site · 80×15
<a href="https://agentmods.dev/skills/meltedinhex/analyst-ai-pack/detecting-sandbox-evasion-behavior"><img src="https://agentmods.dev/badge/skills/meltedinhex/analyst-ai-pack/detecting-sandbox-evasion-behavior.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 689 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 $0.00689
Opus 5 $0.00039 $0.00345
Sonnet 5 $0.00016 $0.00138
Haiku 4.5 $0.00008 $0.00069

Measured 11d ago against content hash a9bd195a46ae, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

detecting-sandbox-evasion-behavior 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 11d 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/detecting-sandbox-evasion-behavior/SKILL.md · 85 lines

What it actually says

Detecting Sandbox Evasion Behavior

When to Use

  • A sample ran inertly in a sandbox and you suspect evasion.
  • You want to enumerate anti-VM, anti-debug, timing, and environment-fingerprinting checks from static strings/imports and/or an API trace.

Do not use this to conclude a sample is benign — evasion is itself a malicious signal, and absence of detected checks does not prove there are none.

Prerequisites

  • The sample (read inertly) and optionally a JSON API trace.

Safety & Handling

  • Read bytes statically; never execute the sample to "see if it evades."

Workflow

Step 1: Scan for evasion indicators

python scripts/analyst.py scan sample.bin

Searches for VM/sandbox artifact strings (VMware, VBOX, vmtoolsd, sbiedll, common sandbox usernames/hostnames), anti-debug APIs (IsDebuggerPresent, CheckRemoteDebuggerPresent, NtQueryInformationProcess), timing stalls (Sleep, GetTickCount, rdtsc), and CPUID checks.

Step 2: Categorize techniques

Group hits into anti-VM, anti-debug, anti-sandbox, and timing/stalling categories.

Step 3: Recommend bypass and report

Suggest analysis adjustments (patch sleeps, hardened VM, hooking) and map findings to ATT&CK.

Validation

  • Detected indicators are grouped by evasion category.
  • Findings distinguish static-string evidence from API-trace evidence when both are provided.
  • Each category maps to an ATT&CK technique/subtechnique.

Pitfalls

  • False positives from benign software that also queries the environment — corroborate.
  • Strings can be obfuscated; absence of plaintext artifacts is not absence of evasion.
  • Confusing a hung sample with deliberate stalling without timing evidence.

References

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. 11d ago First seen · 85 lines · 79 tokens per session scan A a9bd195a46ae

Subscribe to this mod's changes

detecting-sandbox-evasion-behavior 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 689 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.

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