CTF Forensics & Blockchain

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

Additional Resources

• 3d-printing.md - 3D printing forensics (PrusaSlicer binary G-code, QOIF, heatshrink)
• windows.md - Windows forensics (registry, SAM, event logs, recycle bin, USN journal, PowerShell history, Defender MPLog, WMI persistence, Amcache)
• network.md - Network forensics (tcpdump, TLS/SSL keylog decryption, PCAP, SMB3, WordPress, credentials, NTLMv2 cracking, USB HID steno, USB HID mouse/pen drawing recovery, BCD encoding, HTTP file upload exfiltration, packet interval timing encoding, TCP flag covert channel, Brotli decompression bomb seam, DNS trailing byte binary encoding, fake TLS stream extraction with mDNS key and printability merge)
• disk-and-memory.md - Disk/memory forensics (Volatility, disk mounting/carving, VM/OVA/VMDK, coredumps, deleted partitions, ZFS, VMware snapshots, ransomware analysis, GPT GUID encoding, VMDK sparse parsing)
• steganography.md - Image steganography (binary border stego, PDF multi-layer stego, SVG keyframes, PNG reorder, file overlays, 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)
• stego-advanced.md - Advanced steganography (FFT frequency domain, DTMF audio, SSTV+LSB, 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)
• 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))
• 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

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)
vol3 -f memory.dmp windows.info
vol3 -f memory.dmp windows.pslist
vol3 -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.

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
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

• 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 and stego-advanced.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)
vol3 -f memory.dmp windows.pslist
vol3 -f memory.dmp windows.cmdline
vol3 -f memory.dmp windows.netscan
vol3 -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, VMware snapshots, 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.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

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.

Additional Technique Quick References

• Docker image forensics: Config JSON preserves ALL RUN commands even after cleanup. tar xf app.tar then inspect config blob. See linux-forensics.md.
• Linux attack chains: Check auth.log, .bash_history, recent binaries, PCAP. See linux-forensics.md.
• RAID 5 XOR recovery: Two disks of a 3-disk RAID 5 → XOR byte-by-byte to recover the third: bytes(a ^ b for a, b in zip(disk1, disk3)). See disk-and-memory.md.
• PowerShell ransomware: Extract scripts from minidump, find AES key, decrypt SMTP attachment. See disk-and-memory.md.
• Linux ransomware + memory dump: If Volatility is unreliable, recover AES key via raw-memory candidate scanning and magic-byte validation; re-extract zip cleanly to avoid missing files/false negatives. See disk-and-memory.md.
• Deleted partitions: testdisk or kpartx -av. See disk-and-memory.md.
• ZFS forensics: Reconstruct labels, Fletcher4 checksums, PBKDF2 cracking. See disk-and-memory.md.
• Hardware signals: VGA/HDMI TMDS/DisplayPort, Voyager audio, Saleae UART decode, Flipper Zero. See signals-and-hardware.md.
• USB HID mouse drawing: Render relative HID movements per draw mode as bitmap; separate modes, skip pen lifts, scale 5-8x. See network.md.
• Side-channel power analysis: Multi-dimensional power traces (positions × guesses × traces × samples). Average across traces, find sample with max variance, select guess with max power at leak point. See signals-and-hardware.md.
• Packet interval timing: Binary data encoded as inter-packet delays in PCAP. Two interval values = two bit values. See network.md.
• BMP bitplane QR: Extract bitplanes 0-2 per RGB channel with NumPy; hidden QR often in bit 1 (not bit 0). See steganography.md.
• Image puzzle reassembly: Edge-match pixel differences between piece borders, greedy placement in grid. See steganography.md.
• Audio FFT notes: Dominant frequencies → musical note names (A-G) spell words. See stego-advanced.md.
• Audio metadata octal: Exiftool comment with underscore-separated octal numbers → decode to ASCII/base64. See stego-advanced.md.
• G-code visualization: Side projections (XZ/YZ) reveal text. See 3d-printing.md.
• Git directory recovery: gitdumper.sh for exposed .git dirs. See linux-forensics.md.
• KeePass v4 cracking: Standard keepass2john lacks v4/Argon2 support; use ivanmrsulja/keepass2john fork or keepass4brute. Generate wordlists with cewl. See linux-forensics.md.
• Cross-channel multi-bit LSB: Different bit positions per RGB channel (R[0], G[1], B[2]) encode hidden data. See stego-advanced.md.
• F5 JPEG DCT detection: Ratio of ±1 to ±2 AC coefficients drops from ~3:1 to ~1:1 with F5; sparse images need secondary ±2/±3 metric. See steganography.md.
• PNG unused palette stego: Unused PLTE entries (not referenced by pixels) carry hidden data in red channel values. See steganography.md.
• Keyboard acoustic side-channel: MFCC features from keystroke audio + KNN classification against labeled reference. 10ms window captures impact transient. See signals-and-hardware.md.
• TCP flag covert channel: 6 TCP flag bits (FIN/SYN/RST/PSH/ACK/URG) = values 0-63, encoding base64 characters. Nonsensical flag combos on a consistent dest port = covert data. See network.md.
• Brotli decompression bomb seam: Compressed bomb has repeating blocks; flag breaks the pattern at a seam. Compare adjacent blocks to find discontinuity, decompress only that region. See network.md.
• Git reflog/fsck squash recovery: git rebase --squash leaves orphaned objects recoverable via git fsck --unreachable --no-reflogs. See linux-forensics.md.
• DNS trailing byte binary: Extra bytes (0x30/0x31) appended after DNS question structure encode binary bits; 8-bit MSB-first chunks → ASCII. See network.md.
• Fake TLS + mDNS key + printability merge: TCP stream disguised as TLS hides ZIP; XOR key from mDNS TXT record; merge two decrypted arrays by selecting printable characters. See network.md.
• Seed-based pixel permutation stego: Deterministic pixel shuffle (Fisher-Yates with known seed) + multi-bitplane interleaved LSB extraction from Y channel → hidden QR code. See steganography.md.

HTTP Exfiltration in PCAP

Quick path: tshark --export-objects http,/tmp/objects extracts uploaded files instantly. Check for multipart POST uploads, unusual User-Agent strings, and exfiltrated files (images with flag text). See network.md.

Common Encodings

echo "base64string" | base64 -d
echo "hexstring" | xxd -r -p
# ROT13: tr 'A-Za-z' 'N-ZA-Mn-za-m'

ROT18: ROT13 on letters + ROT5 on digits. Common final layer in multi-stage forensics. See linux-forensics.md for implementation.