dfir

DFIR

Investigate security incidents by analyzing event logs, network captures, and filesystem artifacts. Detect and reconstruct AD attack chains.

Techniques

Domain	Key Capabilities
Windows Event Logs	EVTX parsing, Event ID correlation, logon tracking, privilege enumeration
Network Forensics	PCAP analysis, NTLM extraction, LLMNR/NBT-NS poisoning detection, relay identification
Filesystem Forensics	MFT parsing, Prefetch analysis, VSS artifact recovery, Linux persistence, timeline reconstruction
AD Attack Detection	Kerberoasting, AS-REP roasting, NTDS dump, NTLM relay, credential theft
Memory Forensics	Volatility3 analysis: process trees, file extraction, SID resolution, command lines
Hash Analysis	NTLMv2 hash construction from pcap, offline cracking validation

Workflow

1. Inventory evidence — List all artifacts (EVTX, pcap, MFT, prefetch, registry)
2. Parse structured data — EVTX with python-evtx, pcap with tshark, MFT with analyzeMFT
3. Identify attack indicators — Key Event IDs, suspicious traffic patterns, anomalous files
4. Correlate across sources — Match timestamps, IPs, LogonIDs, and process IDs across artifacts
5. Reconstruct timeline — Build chronological attack chain with UTC timestamps
6. Answer investigative questions — Map findings to specific incident response queries

Tools

pip install python-evtx windowsprefetch analyzeMFT
brew install wireshark p7zip hashcat

Tool	Purpose
python-evtx	Parse Windows .evtx files
tshark	CLI pcap analysis (NTLM, LLMNR, SMB filters)
analyzeMFT	Parse NTFS Master File Table
windowsprefetch	Parse Windows prefetch files (Windows host only)
hashcat	Hash cracking (NTLMv2 mode 5600, Kerberos mode 13100/18200)
volatility3	Memory dump analysis (pstree, filescan, dumpfiles, getsid, cmdline)
7z	Extract AES-encrypted evidence ZIPs

Quick Reference: Key Event IDs

Event ID	Log	Indicates
4624	Security	Successful logon (check Type + IP mismatch)
4768	Security	TGT request (PreAuthType=0 → AS-REP roast)
4769	Security	TGS request (EncType=0x17 → Kerberoast)
4799	Security	Group membership enumerated (VSS/ntdsutil)
5140	Security	Network share accessed
7036	System	Service state change (VSS start → NTDS dump)
325/326/327	Application	ESENT database create/detach/close
330	Application	ESENT database file info
3006/3008	DNS Client Events	DNS query sent/response received (malicious domain lookups)
106/200	Task Scheduler	Scheduled task created/executed (persistence via schtasks)

Reference

• windows-event-analysis.md — EVTX parsing patterns and AD attack detection
• network-forensics.md — PCAP analysis for NTLM, LLMNR, relay detection
• filesystem-forensics.md — MFT, Prefetch, VSS artifact analysis

Critical Rules

• Answer formatting: When forensics questions ask for "the value" of a code variable (e.g., PHP $shell), include language-specific string delimiters and terminators (e.g., 'value'; not just value). Check placeholder hints for format clues.
• For malicious Office OOXML, inspect more than VBA streams: attackers may split staged Base64 or script content across drawing/object descriptors, shared strings, named cells, and hidden UserForm control captions/values.
• When a VBA byte array starts with an fnstenv/pop decoder stub, convert signed integers to raw bytes and test a Shikata-style rolling XOR decode before treating the shellcode as corrupt.
• For legacy Excel BIFF/XLS malware, inspect BOUNDSHEET records for hidden or very hidden worksheets and specifically check for Excel 4.0 macro sheets; changing the hidden-state byte or parsing the sheet directly can expose staged strings and flag fragments that never appear in normal workbook views.
• For webshell traffic in PCAPs, recover static keys from the uploaded server-side code first, then decrypt operator tasking before chasing later payloads; if a dropped XOR key file is referenced by a shellcode stage, verify where the encoded region actually starts instead of XORing the whole blob from offset zero.
• PowerShell stager pattern (in-place reverse + base64 + IEX): when a stage-1 PS script does [array]::Reverse($charArr) followed by FromBase64String("$charArr"), the -join line is often a red herring — string interpolation of a char array uses $OFS=' ' and FromBase64String tolerates whitespace. Reverse the original base64 string (not the joined-with-spaces version) and decode to get stage 2.
• Multi-fragment flag exfil: forensic challenges may split a flag across (a) a hardcoded $partN in the malware that is defined but never referenced (often base64'd), and (b) a field of the captured C2 POST body. Decrypt the body with the static AES key from the leaked stage-2 source (PowerShell Encrypt-String puts IV‖ciphertext then base64-wraps); inspect every JSON field for further base64.
• All timestamps in UTC — convert from local time zones in pcap/logs. AM/PM trap: 12:XX AM = 00:XX (midnight), 12:XX PM = 12:XX (noon). 12 AM ≠ 01:00.
• Parse EVTX with python-evtx (XML namespace: http://schemas.microsoft.com/win/2004/08/events/event)
• Use tshark for pcap (not scapy for large files) — filter with -Y display filters
• Decompress Win10 prefetch (MAM\x04 header) with dissect.util.compression.lzxpress_huffman
• For AES-encrypted ZIPs (compression method 99), use 7z not unzip