Ctf Forensics

CTF Forensics & Blockchain

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

Prerequisites

Python packages (all platforms):

pip install volatility3 Pillow numpy matplotlib

Linux (apt):

apt install binwalk foremost libimage-exiftool-perl tshark sleuthkit \
  ffmpeg steghide testdisk john pcapfix

macOS (Homebrew):

brew install binwalk exiftool wireshark sleuthkit ffmpeg \
  testdisk john-jumbo

Ruby gems (all platforms):

gem install zsteg

Additional Resources

• 3d-printing.md - 3D printing forensics (PrusaSlicer binary G-code, QOIF, heatshrink)
• windows.md - Windows forensics (registry, SAM, event logs, recycle bin, NTFS alternate data streams, USN journal, PowerShell history, Defender MPLog, WMI persistence, Amcache)
• network.md - Network forensics basics (tcpdump, TLS/SSL keylog decryption, TLS master key extraction from coredump, Wireshark, PCAP, port scanning, SMB3 decryption, 5G/NR protocols, WordPress recon, credentials, USB HID steno, BCD encoding, HTTP file upload exfiltration, split archive reassembly via timestamp ordering)
• network-advanced.md - Advanced network forensics (packet interval timing encoding, NTLMv2 hash cracking, TCP flag covert channel, DNS last-byte steganography, DNS trailing byte binary encoding, multi-layer PCAP with XOR + ZIP and mDNS key, Brotli decompression bomb seam analysis, SMB RID recycling via LSARPC, Timeroasting MS-SNTP hash extraction, dnscat2 reassembly, RADIUS shared secret cracking, RC4 stream identification, ICMP payload byte rotation, ICMP ping time-delay covert channel)
• peripheral-capture.md - USB/HID/Bluetooth peripheral traffic reconstruction (USB HID mouse/pen drawing recovery, USB HID keyboard capture decoding, USB keyboard LED Morse code exfiltration, USB HID keyboard arrow key navigation tracking, Bluetooth RFCOMM packet reassembly)
• disk-and-memory.md - Core disk/memory forensics (Volatility, disk mounting/carving, VM/OVA/VMDK, VMware snapshots, GIMP raw memory dump visual inspection, coredumps, Windows KAPE triage, PowerShell ransomware, Android forensics, Docker container forensics, cloud storage forensics, BSON reconstruction, TrueCrypt/VeraCrypt mounting)
• disk-advanced.md - Advanced disk and memory techniques (deleted partitions, ZFS forensics, GPT GUID encoding, VMDK sparse parsing, memory dump string carving, ransomware key recovery, WordPerfect macro XOR, minidump ISO 9660 recovery, APFS snapshot recovery, RAID 5 XOR recovery, HFS+ resource fork recovery, Kyoto Cabinet hash DB forensics, SQLite edit history reconstruction)
• disk-recovery.md - Disk recovery and extraction patterns (LUKS master key recovery, PRNG timestamp seed brute-force, VBA macro binary recovery, FemtoZip decompression, XFS filesystem reconstruction, tar duplicate entry extraction, nested matryoshka filesystem extraction, anti-carving via null byte interleaving, BTRFS subvolume/snapshot recovery, FAT16 free space data recovery, FAT16 deleted file recovery via Sleuth Kit fls/icat, ext2 orphaned inode recovery via fsck, corrupted ZIP header repair)
• steganography.md - General steganography (binary border stego, PDF multi-layer stego, SVG keyframes, PNG reorder, file overlays, GIF frame diff Morse code, GZSteg + spammimic, spreadsheet frequency recovery, Kitty terminal graphics protocol decoding, ANSI escape sequence steganography, autostereogram solving, two-layer byte+line interleaving, multi-stream video container stego, progressive PNG layered XOR decryption, QR code reconstruction from curved reflection)
• stego-image.md - Image-specific steganography (JPEG unused DQT table LSB, BMP bitplane QR extraction, image puzzle reassembly, F5 JPEG DCT ratio detection, PNG unused palette entry stego, QR code tile reconstruction, seed-based pixel permutation + multi-bitplane QR, JPEG thumbnail pixel-to-text mapping, conditional LSB with pixel filtering, JPEG slack space, nearest-neighbor interpolation stego, RGB parity steganography)
• stego-advanced.md - Advanced steganography part 1: audio and signal techniques (FFT frequency domain, DTMF audio, SSTV+LSB, DotCode barcode, custom frequency dual-tone keypad, multi-track audio differential subtraction, cross-channel multi-bit LSB, audio FFT musical notes, audio metadata octal encoding, nested tar whitespace encoding, DeepSound audio stego with password cracking, audio waveform binary encoding, audio spectrogram hidden QR)
• stego-advanced-2.md - Advanced steganography part 2: video, image transform, and format-specific techniques (video frame accumulation, reversed audio, video frame averaging, JPEG XL TOC permutation steganography, Arnold's Cat Map descrambling, high-resolution SSTV custom FM demodulation, MJPEG FFD9 trailing byte stego, EXIF zlib + Stegano pixel patterns, PDF xref covert channel, ANSI escape code stego, pixel-wise ECB deduplication)
• linux-forensics.md - Linux/app forensics (log analysis, Docker image forensics, attack chains, browser credentials, Firefox history, TFTP, TLS weak RSA, USB audio, Git directory recovery, KeePass v4 cracking, Git reflog/fsck squash recovery, browser artifact analysis (Chrome/Chromium/Firefox history, cookies, downloads, local storage, session restore), corrupted git blob repair via byte brute-force, VBA macro Excel cell data to ELF binary extraction, Python in-memory source recovery via pyrasite)
• signals-and-hardware.md - Hardware signal decoding with decode code (VGA frame parsing, HDMI TMDS symbol decode, DisplayPort 8b/10b + LFSR descrambler), Voyager Golden Record audio, Saleae Logic 2 UART decode, Flipper Zero .sub files, side-channel power analysis (DPA), keyboard acoustic side-channel, CD audio disc image steganography (CIRC de-interleaving + spiral rendering), caps-lock LED Morse code from video, Linux input_event keylogger dump parsing, serial UART from WAV audio, USB MIDI Launchpad grid reconstruction

When to Pivot

• If you recover an encrypted blob and the hard part becomes RSA, AES, or lattice work, switch to /ctf-crypto.
• If the evidence really points to malware staging, beacon config extraction, or packed samples, switch to /ctf-malware.
• If the artifact is a web app backup or API dump and the remaining problem is application logic, switch to /ctf-web.
• If the forensic evidence is really an encoding puzzle, steganography trick, or esoteric format rather than true forensics, switch to /ctf-misc.
• If you need to trace infrastructure, attribute actors, or investigate public records from forensic findings, switch to /ctf-osint.
• If the recovered artifact is a compiled binary or firmware that needs disassembly and analysis, switch to /ctf-reverse.

Quick Start Commands

# File analysis
file suspicious_file
exiftool suspicious_file     # Metadata
binwalk suspicious_file      # Embedded files
strings -n 8 suspicious_file
hexdump -C suspicious_file | head  # Check magic bytes

# Disk forensics
sudo mount -o loop,ro image.dd /mnt/evidence
fls -r image.dd              # List files
photorec image.dd            # Carve deleted files

# Memory forensics (Volatility 3)
vol -f memory.dmp windows.info
vol -f memory.dmp windows.pslist
vol -f memory.dmp windows.filescan

See disk-and-memory.md for full Volatility plugin reference, VM forensics, and coredump analysis.

Log Analysis

grep -iE "(flag|part|piece|fragment)" server.log     # Flag fragments
grep "FLAGPART" server.log | sed 's/.*FLAGPART: //' | uniq | tr -d '\n'  # Reconstruct
sort logfile.log | uniq -c | sort -rn | head         # Find anomalies

See linux-forensics.md for Linux attack chain analysis and Docker image forensics.

Windows Event Logs (.evtx)

Key Event IDs:

• 1001 - Bugcheck/reboot
• 1102 - Audit log cleared
• 4720 - User account created
• 4781 - Account renamed

RDP Session IDs (TerminalServices-LocalSessionManager):

• 21 - Session logon succeeded
• 24 - Session disconnected
• 1149 - RDP auth succeeded (RemoteConnectionManager, has source IP)

import Evtx.Evtx as evtx
with evtx.Evtx("Security.evtx") as log:
    for record in log.records():
        print(record.xml())

See windows.md for full event ID tables, registry analysis, SAM parsing, USN journal, and anti-forensics detection.

• NTFS Alternate Data Streams (ADS): Hidden data attached to files via named NTFS streams. Invisible to dir/Explorer. Detect with fls -r image.dd | grep ":", extract with icat. See windows.md.

When Logs Are Cleared

If attacker cleared event logs, use these alternative sources:

1. USN Journal ($J) - File operations timeline (MFT ref, timestamps, reasons)
2. SAM registry - Account creation from key last_modified timestamps
3. PowerShell history - ConsoleHost_history.txt (USN DATA_EXTEND = command timing)
4. Defender MPLog - Separate log with threat detections and ASR events
5. Prefetch - Program execution evidence
6. User profile creation - First login time (profile dir in USN journal)

See windows.md for detailed parsing code and anti-forensics detection checklist.

Steganography

steghide extract -sf image.jpg -p ""
zsteg image.png              # PNG/BMP analysis
stegsolve                    # Visual analysis

• Binary border stego: Black/white pixels in 1px image border encode bits clockwise

• FFT frequency domain: Image data hidden in 2D FFT magnitude spectrum; try np.fft.fft2 visualization

• DTMF audio: Phone tones encoding data; decode with multimon-ng -a DTMF

• Multi-layer PDF: Check hidden comments, post-EOF data, XOR with keywords, ROT18 final layer

• SSTV + LSB: SSTV signal may be red herring; check 2-bit LSB of audio samples with stegolsb

• SVG keyframes: Animation keyTimes/values attributes encode binary/Morse via fill color alternation

• PNG chunk reorder: Fix chunk order: IHDR → ancillary → IDAT (in order) → IEND

• File overlays: Check after IEND for appended archives with overwritten magic bytes

• APNG frame extraction: Animated PNG has multiple frames; extract with apngdis or parse fdAT/fcTL chunks. See steganography.md.

• PNG height/CRC manipulation: Modify IHDR height field, brute-force until CRC matches to reveal hidden rows. See steganography.md.

• Pixel coordinate chain stego: Linked-list traversal where R=data byte, G/B=next pixel coordinates. See stego-image.md.

• AVI frame differential: XOR consecutive video frames to reveal hidden data in pixel differences. See stego-image.md.

• Custom freq DTMF: Non-standard dual-tone frequencies; generate spectrogram first (ffmpeg -i audio -lavfi showspectrumpic), map custom grid to keypad digits, decode variable-length ASCII

• JPEG DQT LSB: Unused quantization tables (ID 2, 3) carry LSB-encoded data; access via Image.open().quantization and extract bit 0 from each of 64 values

• Multi-track audio subtraction: Two nearly-identical audio tracks in MKV/video; sox -m a0.wav "|sox a1.wav -p vol -1" diff.wav cancels shared content, flag appears in spectrogram of difference signal (5-12 kHz band)

• Packet interval timing: Identical packets with two distinct interval values (e.g., 10ms/100ms) encode binary; filter by interface, compute inter-packet deltas, threshold to bits

See steganography.md, stego-advanced.md, and stego-advanced-2.md for full code examples and decoding workflows.

PDF Analysis

exiftool document.pdf        # Metadata (often hides flags!)
pdftotext document.pdf -     # Extract text
strings document.pdf | grep -i flag
binwalk document.pdf         # Embedded files

Advanced PDF stego (Nullcon 2026 rdctd): Six techniques -- invisible text separators, URI annotations with escaped braces, Wiener deconvolution on blurred images, vector rectangle QR codes, compressed object streams (mutool clean -d), document metadata fields.

See steganography.md for full PDF steganography techniques and code.

Disk / VM / Memory Forensics

# Disk images
sudo mount -o loop,ro image.dd /mnt/evidence
fls -r image.dd && photorec image.dd

# VM images (OVA/VMDK)
tar -xvf machine.ova
7z x disk.vmdk -oextracted "Windows/System32/config/SAM" -r

# Memory (Volatility 3)
vol -f memory.dmp windows.pslist
vol -f memory.dmp windows.cmdline
vol -f memory.dmp windows.netscan
vol -f memory.dmp windows.dumpfiles --physaddr <addr>

# String carving
strings -a -n 6 memdump.bin | grep -E "FLAG|SSH_CLIENT|SESSION_KEY"

# Coredump
gdb -c core.dump  # info registers, x/100x $rsp, find "flag"

See disk-and-memory.md for full Volatility plugin reference, VM forensics, and VMware snapshots. See disk-advanced.md for deleted partition recovery, ZFS forensics, and ransomware analysis.

Windows Password Hashes

# Extract with impacket, crack with hashcat -m 1000
python -c "from impacket.examples.secretsdump import *; SAMHashes('SAM', LocalOperations('SYSTEM').getBootKey()).dump()"

See windows.md for SAM details and network-advanced.md for NTLMv2 cracking from PCAP.

Bitcoin Tracing

• Use mempool.space API: https://mempool.space/api/tx/<TXID>
• Peel chain: ALWAYS follow LARGER output; round amounts indicate peels

Uncommon File Magic Bytes

Common Flag Locations

• PDF metadata fields (Author, Title, Keywords)
• Image EXIF data
• Deleted files (Recycle Bin $R files)
• Registry values
• Browser history
• Log file fragments
• Memory strings

WMI Persistence Analysis

Pattern (Backchimney): Malware uses WMI event subscriptions for persistence (MITRE T1546.003).

python PyWMIPersistenceFinder.py OBJECTS.DATA

• Look for FilterToConsumerBindings with CommandLineEventConsumer
• Base64-encoded PowerShell in consumer commands
• Event filters triggered on system events (logon, timer)

See windows.md for WMI repository analysis details.

Network Forensics Quick Reference

• TFTP netascii: Binary transfers corrupted; fix with data.replace(b'\r\n', b'\n').replace(b'\r\x00', b'\r')
• TLS keylog decryption: Import SSLKEYLOGFILE or RSA private key into Wireshark (Edit → Preferences → Protocols → TLS)
• TLS weak RSA: Extract cert, factor modulus, generate private key with rsatool, add to Wireshark
• USB audio: Extract isochronous data with tshark -e usb.iso.data, import as raw PCM in Audacity
• NTLMv2 from PCAP: Extract server challenge + NTProofStr + blob from NTLMSSP_AUTH, brute-force
• WPA/WEP WiFi decryption: aircrack-ng -w wordlist capture.pcap cracks WPA handshake; WEP cracked with enough IVs. See network.md.
• PCAP repair: pcapfix -d corrupted.pcap repairs broken PCAP headers/checksums for Wireshark loading. See network.md.
• USB HID keyboard decoding: Extract 8-byte HID reports from USB captures; byte 2 = keycode, byte 0 = modifiers (Shift). See peripheral-capture.md.
• dnscat2 reassembly: Decode hex/base32 subdomain labels, strip 9-byte dnscat2 header, deduplicate retransmissions, reassemble payload. See network-advanced.md.
• USB keyboard LED exfiltration: Host-to-device HID SET_REPORT packets toggle Caps Lock LED. Timing encodes Morse code. See peripheral-capture.md.

See network.md for SMB3 decryption, credential extraction, and linux-forensics.md for full TLS/TFTP/USB workflows.

Browser Forensics

• Chrome/Edge: Decrypt Login Data SQLite with AES-GCM using DPAPI master key
• Firefox: Query places.sqlite -- SELECT url FROM moz_places WHERE url LIKE '%flag%'

See linux-forensics.md for full browser credential decryption code.