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Community / AGENT SKILL
analyzing-elf-binaries-on-linux
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Statically analyzes Linux ELF malware: ELF header and sections, dynamic symbols and imports, segment permissions, embedded strings, and packing indicators to infer capability without execution. Activates for requests to analyze an ELF binary, Linux malware, or shared object.
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Original instructions from the publisher’s SKILL.md
# Analyzing ELF Binaries on Linux ## When to Use - You have a Linux executable or shared object and need to assess it statically. - You want to read the ELF header, segments, dynamic symbols, and strings to infer behavior. - You are checking for static linking, stripped symbols, or packing. **Do not use** symbol absence as proof of nothing — stripped or statically linked Go/Rust binaries hide structure; switch to disassembly when static metadata is thin. ## Prerequisites - `readelf`/`nm`/`strings` (binutils) or `pyelftools` (`pip install pyelftools`). - The sample in neutralized form inside the lab. ## Safety & Handling - Static only: parse the file; do not set it executable or run it. ## Workflow ### Step 1: Read the ELF header ```bash python scripts/analyst.py analyze sample.elf ``` Note class (ELF32/64), endianness, type (EXEC/DYN/REL), machine (x86-64, ARM, MIPS), and whether it is stripped. ### Step 2: Examine segments and section permissions Writable+executable segments, or a single large segment, suggest packing or self-modifying code. Compare `PT_LOAD` permissions against expectations. ### Step 3: Inspect dynamic symbols and needed libraries Imported functions hint at capability: `socket`/`connect` (network), `ptrace` (anti-debug or injection), `fork`/`execve` (process control), `crypt`/`EVP_*` (encryption). ### Step 4: Detect static linking and packing Static binaries lack a dynamic symbol table and `NEEDED` entries. High whole-file entropy and a tiny section table suggest a packer (e.g. UPX leaves `UPX!` markers). ### Step 5: Skim strings and constructors Check `.init_array`/constructors (code before `main`), and strings for paths, URLs, and shell commands. ## Validation - Header `type` and segment permissions are consistent with the inferred behavior. - Imported symbols correspond to plausible capabilities. - Packing call (entropy + missing sections) matches the strings observed. ## Pitfalls - Assuming dynamic symbols are complete — they only cover imported/exported names, not internal functions. - Treating a stripped Go binary as "empty"; its structure lives in runtime metadata, not the symbol table. - Ignoring constructors/`.init_array`, which run before `main`. ## References - See [`references/api-reference.md`](references/api-reference.md) for the ELF analyzer. - ELF/System V ABI spec and pyelftools (linked in frontmatter).
Skill folder
Files included alongside SKILL.md in the publisher’s repository.