---
id: ljagiello/ctf-skills/ctf-malware
version: "125f033a"
license: MIT
install: manual
updated: 2026-07-24
---

# ctf-malware — ctf-malware equips you with techniques for dissecting malware in CTF competitions, covering obfuscated scripts, binary analysis, network traffic decryption, and evasion detection. It guides you through static analysis with tools like YARA and Capstone, dynamic analysis with strace and ltrace, and memory forensics with Volatility, plus custom crypto protocol identification and malware configuration extraction.

Publisher: ljagiello · Stars: 2840 · Updated: 2026-07-24

Install (manual): `git clone https://github.com/ljagiello/ctf-skills`

## SKILL.md

# CTF Malware & Network Analysis

Quick reference for malware analysis CTF challenges. Each technique has a one-liner here; see supporting files for full details with code.

## Prerequisites

**Python packages (all platforms):**
```bash
pip install yara-python pefile capstone oletools unicorn pycryptodome \
  volatility3 dissect.cobaltstrike
```

**Linux (apt):**
```bash
apt install strace ltrace tshark binwalk binutils
```

**macOS (Homebrew):**
```bash
brew install wireshark binwalk binutils ghidra
```

**Manual install:**
- dnSpy — [GitHub](https://github.com/dnSpy/dnSpy), .NET decompiler (Windows)

## Additional Resources

- [scripts-and-obfuscation.md](scripts-and-obfuscation.md) - JavaScript deobfuscation, PowerShell analysis, eval/base64 decoding, junk code detection, hex payloads, Debian package analysis, dynamic analysis techniques (strace/ltrace, network monitoring, memory string extraction, automated sandbox execution), YARA rules for malware detection, shellcode analysis (Unicorn Engine, Capstone), memory forensics for malware (Volatility 3 malfind, process injection detection), anti-analysis techniques (VM detection, timing evasion, API hashing, process injection), trojanized plugin analysis with custom alphabet C2 decoding
- [c2-and-protocols.md](c2-and-protocols.md) - C2 traffic patterns, custom crypto protocols, RC4 WebSocket, DNS-based C2, network indicators, PCAP analysis, AES-CBC, encryption ID, Telegram bot recovery, Poison Ivy RAT Camellia decryption
- [pe-and-dotnet.md](pe-and-dotnet.md) - PE analysis (peframe, pe-sieve, pestudio), .NET analysis (dnSpy, AsmResolver), LimeRAT extraction, sandbox evasion, malware config extraction, PyInstaller+PyArmor

---

## When to Pivot

- If the sample is really just a normal crackme, packed challenge binary, or custom VM with no malware behavior, switch to `/ctf-reverse`.
- If the main job is network reconstruction, disk carving, or host artifact recovery, switch to `/ctf-forensics`.
- If the challenge turns into public attribution or infrastructure tracing, switch to `/ctf-osint`.

## Quick Start Commands

```bash
# Static analysis
file suspicious_file
strings -n 8 suspicious_file | head -50
xxd suspicious_file | head -20

# PE analysis
python3 -c "import pefile; pe=pefile.PE('mal.exe'); print(pe.dump_info())" | head
peframe mal.exe

# Dynamic analysis (sandboxed!)
strace -f -s 200 ./suspicious 2>&1 | head -100
ltrace ./suspicious 2>&1 | head -50

# Network indicators
strings suspicious_file | grep -E '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'
strings suspicious_file | grep -iE 'http|ftp|ws://'

# YARA scan
yara -r rules.yar suspicious_file
```

## Obfuscated Scripts

- Replace `eval`/`bash` with `echo` to print underlying code; extract base64/hex blobs and analyze with `file`. See [scripts-and-obfuscation.md](scripts-and-obfuscation.md).

## JavaScript & PowerShell Deobfuscation

- JS: Replace `eval` with `console.log`, decode `unescape()`, `atob()`, `String.fromCharCode()`.
- PowerShell: Decode `-enc` base64, replace `IEX` with output. See [scripts-and-obfuscation.md](scripts-and-obfuscation.md).

## Junk Code Detection

- NOP sleds, push/pop pairs, dead writes, unconditional jumps to next instruction. Filter to extract real `call` targets. See [scripts-and-obfuscation.md](scripts-and-obfuscation.md).

## PCAP & Network Analysis

```bash
tshark -r file.pcap -Y "tcp.stream eq X" -T fields -e tcp.payload
```

Look for C2 on unusual ports. Extract IPs/domains with `strings | grep`. See [c2-and-protocols.md](c2-and-protocols.md).

## Custom Crypto Protocols

- Stream ciphers share keystream state for both directions; concatenate ALL payloads chronologically.
- ChaCha20 keystream extraction: send nullbytes (0 XOR anything = anything). See [c2-and-protocols.md](c2-and-protocols.md).

## C2 Traffic Patterns

- Beaconing, DGA, DNS tunneling, HTTP(S) with custom headers, encoded payloads. See [c2-and-protocols.md](c2-and-protocols.md).

## RC4-Encrypted WebSocket C2

- Remap port with `tcprewrite`, add RSA key for TLS decryption, find RC4 key in binary. See [c2-and-protocols.md](c2-and-protocols.md).

## Identifying Encryption Algorithms

- AES: `0x637c777b` S-box; ChaCha20: `expand 32-byte k`; TEA/XTEA: `0x9E3779B9`; RC4: sequential S-box init. See [c2-and-protocols.md](c2-and-protocols.md).

## AES-CBC in Malware

- Key = MD5/SHA256 of hardcoded string; IV = first 16 bytes of ciphertext. See [c2-and-protocols.md](c2-and-protocols.md).

## PE Analysis

```bash
peframe malware.exe      # Quick triage
pe-sieve                 # Runtime analysis
pestudio                 # Static analysis (Windows)
```

See [pe-and-dotnet.md](pe-and-dotnet.md).

## .NET Malware Analysis

- Use dnSpy/ILSpy for decompilation; AsmResolver for programmatic analysis. LimeRAT C2: AES-256-ECB with MD5-derived key. See [pe-and-dotnet.md](pe-and-dotnet.md).

## Malware Configuration Extraction

- Check .data section, PE/.NET resources, registry keys, encrypted config files. See [pe-and-dotnet.md](pe-and-dotnet.md).

## Sandbox Evasion Checks

- VM detection, debugger detection, timing checks, environment checks, analysis tool detection. See [pe-and-dotnet.md](pe-and-dotnet.md).

## Anti-Analysis Techniques

VM detection (CPUID, MAC prefix, registry, disk size), timing evasion (sleep/RDTSC sandbox detection), API hashing (ROR13/DJB2/CRC32 + hashdb lookup), process injection (hollowing, APC, CreateRemoteThread), environment checks. See [scripts-and-obfuscation.md](scripts-and-obfuscation.md#anti-analysis-techniques).

## Trojanized Plugin Analysis

Diff malicious plugin against official release to find injected code in try/except blocks. Custom alphabet rotation (`C[(C.index(ch) - offset) % len(C)]`) decodes C2 domain, XOR decodes endpoint path. See [scripts-and-obfuscation.md](scripts-and-obfuscation.md#trojanized-plugin-analysis-with-custom-alphabet-c2-decoding-inshack-2018).

## PyInstaller + PyArmor Unpacking

- `pyinstxtractor.py` to extract, PyArmor-Unpacker for protected code. See [pe-and-dotnet.md](pe-and-dotnet.md).

## Telegram Bot Evidence Recovery

- Use bot token from malware source to call `getUpdates` and `getFile` APIs. See [c2-and-protocols.md](c2-and-protocols.md).

## Debian Package Analysis

```bash
ar -x package.deb && tar -xf control.tar.xz  # Check postinst scripts
```

See [scripts-and-obfuscation.md](scripts-and-obfuscation.md).

## YARA Rules for Malware Detection

Write YARA rules to match byte patterns, strings, and regex against files or memory dumps. Detect XOR loops (`{31 ?? 80 ?? ?? 4? 75}`), base64 blobs, encoded PowerShell. Use `yarac` to compile for faster scanning. See [scripts-and-obfuscation.md](scripts-and-obfuscation.md#yara-rules-for-malware-detection).

## Shellcode Analysis

Disassemble with `objdump -b binary -m i386:x86-64`, emulate with Unicorn Engine (hook syscalls safely), or use Capstone for programmatic disassembly. Look for XOR decoder stubs. See [scripts-and-obfuscation.md](scripts-and-obfuscation.md#shellcode-analysis).

## Memory Forensics for Malware

`vol3 windows.malfind` detects injected code (PAGE_EXECUTE_READWRITE without mapped file). `windows.pstree` reveals suspicious parent-child relationships. YARA scan memory with `yarascan.YaraScan`. See [scripts-and-obfuscation.md](scripts-and-obfuscation.md#memory-forensics-for-malware).

## Network Indicators Quick Reference

```bash
strings malware | grep -E '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'
tshark -r capture.pcap -Y "dns.qry.name" -T fields -e dns.qry.name | sort -u
```


[View on SkillFed](https://skillfed.io/ljagiello/ctf-skills/ctf-malware) · [View on GitHub](https://github.com/ljagiello/ctf-skills)