High-level approach (one-liner)
I would implement an evidence-first logging pipeline: collect comprehensive sources mapped to STRIDE, store immutably with cryptographic tamper-evidence, enforce strict retention and access controls, and formalize chain-of-custody for forensic use.
Logs to collect (mapped examples)
- Tampering (Tamper): EDR file/system FIM events, OS auditd/Windows Sysmon, application integrity checksums, file metadata, container runtime logs, periodic filesystem snapshots, host-based hashes.
- Repudiation (Repudiation): Authentication/SSO/MFA logs, privileged access sessions (audit/video), API keys usage, command history, code repo commits, CI/CD audit logs.
- Information disclosure (Information Disclosure): Proxy/HTTP logs, DLP alerts, cloud object access (S3/Azure Blob) with object-level events, network flows (NetFlow/Zeek), packet captures for high-risk windows.
Retention & tiering
- Hot (SIEM searchable): 90–180 days for auth, EDR, proxy.
- Warm (archive): 1–3 years for audit/auth logs, system images.
- Cold (legal/forensic): 7+ years or per regulatory needs for incriminating evidence (financial/PII).
Retention policy tied to risk, regulatory requirements, and storage tiering.
Secure storage & tamper-proofing
- Use append-only immutable stores: WORM on-prem, Object Lock + Governance (S3 Object Lock with legal hold) or immutable Azure Blob.
- Cryptographic signing: HMAC/SHA-256 per log chunk + periodic Merkle-tree root signed by a private key in an HSM.
- Remote logging: send logs over TLS to isolated collector network segment; keep copies off-host.
- File integrity monitoring with alerts on any log modification.
- Periodic snapshots and cold backups with checksums.
Timestamping & synchronization
- Central NTP/PTP hierarchy, multiple stratum 1/2 sources, NTP authenticated (symmetrical keys) or Roughtime/RFC 3161 time-stamping service.
- RFC 3161 timestamping of critical signed artifacts (hash + timestamp authority) for courtroom-grade time provenance.
Chain-of-custody & investigation process
- Automate initial evidence capture (hash, capture tool/version, operator, timestamp) and append to case record.
- Maintain immutable audit trail: who accessed evidence, actions taken; require multifactor and RBAC for evidence access.
- Use standardized COC forms (digital + signed) including mounting steps, copies made, checksums, storage locations.
- Preserve original as write-blocked image; perform analysis on certified working copies; log every copy/transfer with hashes.
Operational controls & testing
- Regular log integrity audits, quarterly red-team tests, retention/restore drills, and legal/forensic readiness reviews with SOC, legal, and incident response.
This plan balances forensic completeness, tamper-evidence, and legal defensibility appropriate for enterprise-scale incidents mapped to STRIDE.
