Email Security Gateway Logs
Location
Email gateway console (Proofpoint, Mimecast, Barracuda, Cisco IronPort/ESA) or syslog outputDescription
Email security appliance logs recording message routing decisions, spam/phishing verdicts, malware sandbox analysis results, URL click tracking, DMARC/DKIM/SPF authentication results, and DLP policy matches for all inbound and outbound email.
Forensic Value
Email gateway logs are essential for phishing investigations because they record the full verdict chain for every message processed. Sandbox detonation results identify zero-day malicious attachments. URL rewriting and click tracking logs show which users clicked on phishing links and when. DMARC/DKIM/SPF results prove whether spoofed emails passed or failed authentication checks. Quarantine logs identify additional phishing messages from the same campaign that were blocked before reaching users.
Tools Required
Used in Procedures
Related Blockers
Critical Logs Rotated/Overwritten Before Collection
Key log files (Security EVTX, web server access logs, syslog) have been rotated out or overwritten due to aggressive retention settings, high volume, or attacker manipulation. The evidence window for those sources is now closed.
M365/Azure Logs Past Retention Period
Unified Audit Log (UAL) entries in Microsoft 365 or Azure AD sign-in logs have expired beyond the default 90-day (E3) or 180-day (E5) retention window. Historical evidence of initial access, mailbox abuse, or OAuth consent grants is no longer available in the tenant.
SIEM Not Ingesting Relevant Log Sources
The SIEM does not ingest logs from the affected systems, applications, or network segments. Correlation, alerting, and historical search capabilities are unavailable for the evidence sources most relevant to this incident.
Need Data from External Vendor or MSP
Critical evidence resides with a third-party managed service provider, SaaS vendor, or hosting company. Your team has no direct access and must navigate contractual, legal, and technical hurdles to obtain logs or images.
Attacker Used Timestomping, Log Clearing, or Other Anti-Forensics
Evidence of deliberate anti-forensic activity has been found: timestamps modified, event logs cleared, prefetch/shimcache wiped, or tools designed to defeat forensic analysis were executed. Standard timeline analysis may be unreliable.
Regulatory Notification Deadline Approaching
A regulatory reporting deadline (GDPR 72-hour, SEC 4-day, state breach notification, HIPAA) is imminent and the investigation has not yet determined the full scope of data exposure. The team must balance thorough investigation against mandatory disclosure timelines.
Backups May Be Compromised -- Cannot Trust for Recovery
Backup integrity is uncertain. The attacker may have been present in the environment long enough to have compromised backup copies, planted persistence mechanisms in backup images, or encrypted/deleted backup repositories.