analyzing-packed-malware-with-upx-unpacker
Identifies and unpacks UPX-packed and other packed malware samples to expose the original executable code for static analysis. Covers both standard UPX unpacking and handling modified UPX headers that prevent automated decompression. Activates for requests involving malware unpacking, UPX decompression, packer removal, or preparing packed samples for analysis.
84
81%
Does it follow best practices?
Impact
Pending
No eval scenarios have been run
Passed
No known issues
Quality
Discovery
100%Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.
This is an excellent skill description that clearly defines a specific niche (UPX and packer removal for malware analysis), lists concrete capabilities including edge cases (modified UPX headers), and provides explicit activation triggers. It uses proper third-person voice throughout and balances conciseness with sufficient detail for accurate skill selection.
| Dimension | Reasoning | Score |
|---|---|---|
Specificity | Lists multiple specific concrete actions: identifies packed samples, unpacks UPX-packed malware, handles modified UPX headers, exposes original executable code for static analysis. These are concrete, well-defined capabilities. | 3 / 3 |
Completeness | Clearly answers both 'what' (identifies and unpacks UPX-packed and other packed malware, handles modified UPX headers) and 'when' ('Activates for requests involving malware unpacking, UPX decompression, packer removal, or preparing packed samples for analysis'). | 3 / 3 |
Trigger Term Quality | Includes strong natural trigger terms users would actually say: 'UPX', 'packed malware', 'unpacking', 'UPX decompression', 'packer removal', 'packed samples', 'static analysis'. Good coverage of variations a user might use. | 3 / 3 |
Distinctiveness Conflict Risk | Highly distinctive niche focusing specifically on UPX/packer removal for malware analysis. Very unlikely to conflict with other skills given the specialized domain of malware unpacking and modified UPX header handling. | 3 / 3 |
Total | 12 / 12 Passed |
Implementation
62%Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.
The skill provides excellent actionable guidance with executable code and a well-structured multi-step workflow including validation and fallback paths. However, it is significantly bloated with redundant sections (Key Concepts glossary, Tools & Systems descriptions, Common Scenarios that restate the workflow) that explain things Claude already knows. Trimming the glossary, tool descriptions, and redundant scenario would cut the skill nearly in half without losing any actionable value.
Suggestions
Remove the 'Key Concepts' glossary table entirely — Claude already knows what packing, OEP, PUSHAD/POPAD, entropy, and magic bytes are.
Remove or drastically reduce the 'Tools & Systems' section since all tools are already mentioned with context in Prerequisites and the workflow steps.
Collapse the 'Common Scenarios' section into a brief troubleshooting note within Step 3, since it largely restates the workflow with minor additions (double-packing, overlay data).
Consider moving the output format template to a separate reference file if it's needed, or reduce it to a brief structural outline.
| Dimension | Reasoning | Score |
|---|---|---|
Conciseness | The skill is excessively verbose at ~250+ lines. The 'Key Concepts' glossary table explains terms Claude already knows (what packing is, what PUSHAD/POPAD does, what entropy means). The 'Tools & Systems' section redundantly describes tools already mentioned in prerequisites. The 'Common Scenarios' section largely restates the workflow steps. The output format template, while useful, adds significant length. | 1 / 3 |
Actionability | The skill provides fully executable bash commands and Python scripts throughout. The code is copy-paste ready with concrete examples for packer detection, header repair, entropy analysis, and validation. The manual unpacking steps with x64dbg are specific and procedural. | 3 / 3 |
Workflow Clarity | The 5-step workflow is clearly sequenced with explicit validation in Step 5. There's a clear fallback path: try standard UPX → repair headers → manual unpacking with debugger. The validation step checks entropy, imports, and file sizes to confirm successful unpacking. | 3 / 3 |
Progressive Disclosure | Everything is in a single monolithic file with no references to external documents. The Key Concepts table, Tools & Systems section, and Common Scenarios section could be split out or removed entirely. The content is reasonably organized with clear headers but would benefit from being trimmed or split. | 2 / 3 |
Total | 9 / 12 Passed |
Validation
90%Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.
Validation — 10 / 11 Passed
Validation for skill structure
| Criteria | Description | Result |
|---|---|---|
frontmatter_unknown_keys | Unknown frontmatter key(s) found; consider removing or moving to metadata | Warning |
Total | 10 / 11 Passed | |
- Repository
- mukul975/Anthropic-Cybersecurity-Skills
- Commit
c15f73d
- Reviewed
Table of Contents
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