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Detect Data Exfiltration

Category: Security  ·  Sub-category: network-security  ·  Last updated:
Detection and response for data exfiltration over DNS and HTTPS/web channels, and for egress volume anomalies (MITRE ATT&CK T1041, T1048, T1048.003, T1071.004, T1567). Built from the October 2026 compromised-LiteLLM incident, where a stealer POSTed credentials to a lookalike domain. Ships the sigma-pack proxy rule for the known lookalike-domain exfil plus baselined hunts for DNS tunnelling and download/upload-ratio anomalies, keyed off web proxy logs, DNS telemetry (Sysmon Event ID 22, Windows DNS Server Event ID 256, Zeek dns.log), and firewall or NetFlow byte counts, with tuning, false-positive notes, and D3FEND countermeasures. Use when investigating an unexpected outbound connection or credential-stealer beacon, writing DNS or HTTPS exfiltration detections, hunting for data sent to a lookalike domain or over odd protocols, triaging an egress volume spike, or hardening egress after an AI-gateway or supply-chain compromise.
Security AStatic scan found no risk patternsHow grading works ›

From the source SKILL.md

Exfiltration is the stage where stolen data actually leaves the estate, and attackers reach for the channels you already allow outbound: HTTPS to the open web and DNS to a resolver. Both are open almost everywhere, both carry encrypted or encoded payloads happily, and both blend into enormous volumes of legitimate traffic. This skill is defensive: it explains the technique only as far as detection and mitigation require, ships no stealer, tunnelling, or staging tooling, and treats the attacker's transport only as something to catch in your logs.

What this skill does

Detect Data Exfiltration is a community-contributed Claude Code skill in the network-security sub-category. It ships as a SKILL.md file that Claude Code auto-discovers under ~/.claude/skills/detect-data-exfiltration/ and loads when your prompt matches the skill's trigger.

When to invoke it: Use when investigating an unexpected outbound connection or credential-stealer beacon, writing DNS or HTTPS exfiltration detections, hunting for data sent to a lookalike domain or over odd protocols, triaging an egress volume spike, or hardening egress after an AI-gateway or supply-chain compromise.

Who uses this skill

The Detect Data Exfiltration Claude Code skill is built for security engineers, penetration testers, DevSecOps practitioners, and development teams hardening codebases and infrastructure. It's part of ClaudSkills (also referred to as Claude Skills or Claude Code Skills) — the open community-curated registry of 211,000+ SKILL.md files for Anthropic's Claude Code agent and the wider Claude ecosystem (Claude API, Claude Agent SDK).

How to install

Free

Manual install (2 steps)

mkdir -p ~/.claude/skills/detect-data-exfiltration
curl -L https://claudskills.com/skills/detect-data-exfiltration/SKILL.md \
  -o ~/.claude/skills/detect-data-exfiltration/SKILL.md

Or just download SKILL.md directly and drop it into ~/.claude/skills/detect-data-exfiltration/. Claude Code auto-discovers it on next session.

Skills live at ~/.claude/skills/detect-data-exfiltration/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\detect-data-exfiltration\SKILL.md on Windows. See the full install guide for step-by-step instructions.

Telegram

📱 Install from your phone or desktop Telegram

Open @claudskills_bot on Telegram, tap Open Desktop App, and the desktop app installs this skill for you. Or share the bot link with a colleague — they get the same one-tap install. Learn more →

Pro

One-click install via the desktop app

The ClaudSkills desktop app installs any skill directly into ~/.claude/skills/ with one click — no terminal required. Pro starts at $9/mo or $149 lifetime.

Pro

For the full experience including quality scoring and one-click install features for each skill — upgrade to Pro.

See pricing → Download desktop app

Frequently asked questions

How do I install the Detect Data Exfiltration Claude Code skill?
Install via the ClaudSkills desktop app (one click) or copy SKILL.md from the source repository to ~/.claude/skills/detect-data-exfiltration/SKILL.md and restart Claude Code. Both flows are detailed at claudskills.com/install/.
What does the Detect Data Exfiltration skill do?
Detection and response for data exfiltration over DNS and HTTPS/web channels, and for egress volume anomalies (MITRE ATT&CK T1041, T1048, T1048.003, T1071.004, T1567). Built from the October 2026 compromised-LiteLLM incident, where a stealer POSTed credentials to a lookalike domain. Ships the sigma-pack proxy rule for the known lookalike-domain exfil plus baselined hunts for DNS tunnelling and download/upload-ratio anomalies, keyed off web proxy logs, DNS telemetry (Sysmon Event ID 22, Windows DNS Server Event ID 256, Zeek dns.log), and firewall or NetFlow byte counts, with tuning, false-positive notes, and D3FEND countermeasures. Use when investigating an unexpected outbound connection or credential-stealer beacon, writing DNS or HTTPS exfiltration detections, hunting for data sent to a lookalike domain or over odd protocols, triaging an egress volume spike, or hardening egress after an AI-gateway or supply-chain compromise.
Is this skill free to install?
Yes. ClaudSkills is an open registry — every skill keeps its source repository's license, and manual install via copy is free. ClaudSkills Pro ($9/mo, $79/yr, or $149 one-time) adds one-click install via the desktop app and a multi-signal Quality Score.
When should I use the Detect Data Exfiltration skill?
Use Detect Data Exfiltration when your Claude Code task falls under the Security category — specifically in the network security area. Claude Code auto-discovers installed skills and invokes the right one based on the task description, so you can also ask Claude directly (e.g. "use Detect Data Exfiltration" or describe the task and let Claude pick). Browse related skills at /category/security/.
What is a Claude Code skill and how does the Detect Data Exfiltration skill fit in?
A Claude Code skill is a SKILL.md file that lives under ~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Detect Data Exfiltration is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the Security category. Learn more at /learn/what-is-a-claude-skill/.

Attribution & license

Cite this skill

If you reference this skill in a blog post, paper, or documentation, you can cite it as:

APA
umbrasec-labs. (2026). Detect Data Exfiltration [Claude Code skill]. ClaudSkills. https://claudskills.com/skills/detect-data-exfiltration/
BibTeX
@misc{detect-data-exfiltration-2026,
  author    = {umbrasec-labs},
  title     = {Detect Data Exfiltration [Claude Code skill]},
  year      = {2026},
  publisher = {ClaudSkills},
  url       = {https://claudskills.com/skills/detect-data-exfiltration/}
}

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Security scan

Grade A · scanned 2026-10-25 — free static scan against the OWASP Agentic Skills Top 10.

The scan flagged 2 of 10 categories (data-exfil, execution), including a high-severity pattern. Patterns shown inside code fences are weighted as examples rather than instructions — read the grading methodology for what this does and does not guarantee.

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Browse all Security skills in the ClaudSkills registry, or explore these other picks from the same category:

Browse all Security skills → Top 100 skills
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