Domain & DNS Forensics Playbook: Investigate an Account Takeover That Started With a Gmail Change

Hook: When a Gmail change becomes the opening move in a domain hijack

Unexplained traffic drops, sudden DNS changes, or an unexpected domain transfer attempt often trace back to the same root cause: an email account compromise. In 2026, with major providers like Google allowing primary address changes and identity verification systems under strain, threat actors are exploiting email paths to reach registrars, DNS controls and hosting backends. This playbook gives an operational, forensic checklist to tie an email compromise to downstream DNS changes, domain transfer attempts and backend account tampering — plus the exact artifacts you must collect for remediation and legal evidence.

Executive summary (Most important first)

If you suspect an account takeover started with a Gmail change, immediately preserve evidence, freeze domain and DNS controls, and begin a focused log collection and timeline reconstruction. Key pivots to check: Google Account / Workspace audit logs, OAuth grant events, registrar transfer history, WHOIS/RDAP snapshots, DNS zone serials and change timestamps, MX/SPF/DKIM/DMARC histories and backend access logs (cPanel, hosting provider, CDNs). Follow the step-by-step checklist below to prove causality and prepare defensible evidence for remediation and legal action.

Why this matters in 2026 — trends & context

Recent platform changes (January 2026 Gmail primary-address updates) and slower-than-needed adoption of robust identity defenses have created new windows for fraud. Simultaneously, banks and organizations continue to overestimate identity checks — creating opportunity for attackers using stolen or modified email recovery routes. DNS remains the last line of control for brand and traffic integrity; when attackers pivot from email to DNS, the results are catastrophic: zero organic traffic, phishing pages on your domain, email flow disruption and loss of SSL/TLS certificates.

Investigation priorities — what you must do in the first 60 minutes

1. Preserve state: Snapshot registrar and DNS control panels, take screenshots, export any available logs, and do not make unnecessary changes that could overwrite evidence.
2. Lock the domain: If your registrar supports a transfer lock (Registrar-Lock), enable it immediately. Contact registrar abuse/incident response if you cannot access the account.
3. Collect initial network artifacts: Get current WHOIS/RDAP, DNS records (A, CNAME, MX, NS, SOA, TXT), TLS certificate details, and global propagation snapshots.
4. Audit email provider: Review Google Account Security events, Workspace audit logs, OAuth grants, and recent account recovery changes (primary address, recovery phone, recovery email).
5. Notify internal stakeholders and counsel: Legal, PR, and IT must be informed — preserve chain-of-custody and designate an evidence custodian.

Step-by-step forensic checklist

Below is a sequenced checklist for a thorough investigation tying email compromise to DNS and domain tampering. Each step lists artifacts to collect and suggested commands or console locations.

1. Reconstruct the email compromise

• Collect email headers from the victim account for the time window — inbound and outbound (raw headers show Received path and original IPs).
• Export Google Account / Workspace security logs (Security > Login & security events, Admin Console > Audit > Login).
• Record recent OAuth & API token grants (Admin Console > Security > API permissions; Google Account > Security > Third-party access).
• Artifacts to collect: raw message files (.eml), Gmail “Activity” screenshots, OAuth consent receipts, refresh token issuance timestamps.

2. Capture the registrar record and transfer attempts

• Query RDAP/WHOIS now and save the full response (registrar, registrant email, creation/expiry, status flags like clientTransferProhibited).
• Request registrar transaction logs and transfer request emails; look for EPP transfer tickets, authCode requests, or changes to registrant contact fields.
• Artifacts to collect: RDAP JSON export, WHOIS snapshots (timestamped), registrar support ticket transcripts, transfer-approval emails, EPP status changes.
• Suggested commands: whois example.com; curl -s "https://rdap.arin.net/rdap/domain/example.com" (registries vary).

3. Snapshot DNS and zone history

• Collect current DNS records from authoritative nameservers and public resolvers: A, AAAA, CNAME, MX, NS, SOA, TXT.
• Pull zone serial from SOA and compare with historical zone serials (if you host a zone serial log) to identify exact change timestamps.
• Use archived DNS history services (security vendors or DNSDB) to capture record changes over the last 30–90 days; integrate these feeds into your monitoring and observability workflows for faster correlation.
• Artifacts: dig +trace example.com ANY, dig @ns1.registrar.net example.com SOA +noall +answer, DNS zone file exports, DNS provider audit logs (Cloudflare, AWS Route 53, Gandi, etc.).

4. Verify mail routing & authentication artifacts

• Collect MX records and any recent changes; compare SPF, DKIM and DMARC records before and after the incident.
• Obtain authentication failure/success reports from Google (Gmail Delivery/DLP logs) and from your MTA / inbound gateway.
• Artifacts: MX history, SPF/DKIM public keys, DMARC aggregate reports (RUA), forensic reports (RUF), and MTA logs showing message acceptance or rejection.

5. Correlate web and hosting backend access

• Collect web server access and error logs (NGINX/Apache), CMS admin logs (WordPress, Drupal), and hosting control panel logs (cPanel, Plesk).
• Check for new admin users, modified site files, uploaded webshells and changed file timestamps.
• Artifacts: compressed server logs, file integrity hashes (SHA256), CMS user audit exports, and snapshots of modified pages or phishing content.

6. Trace TLS/Certificate changes

• Query Certificate Transparency logs for newly issued certs for your domain in the incident window.
• Collect ACME issuance logs from your CA (Let’s Encrypt, DigiCert) and host forensics logs if new certs were requested.
• Artifacts: CT log entries, cert PEM files, ACME request metadata.

7. Collect registrar, DNS provider and email provider incident logs

• Open incident tickets with registrar and DNS providers and request logs: login IPs, API calls, user agent strings, and account change history.
• Ask Google Workspace support for an audit export if you use Workspace; for consumer Gmail, request account activity and security events via account settings and Google support channels.
• Artifacts: provider audit exports (CSV/JSON), timestamps, IP geolocation of logins, and session tokens where available.

Tying the pieces together — constructing a provable timeline

Collect the artifacts above into a single timeline. Use these correlation anchors:

• Email account change timestamp (Gmail primary address change, recovery email/phone changes, OAuth consent) as the probable initial compromise point.
• Registrar contact/registrant change timestamps or transfer-auth requests following the email change.
• DNS SOA serial increment or provider audit entries showing zone edits.
• Hosting or CMS admin changes and new file timestamps matching the DNS or registrar events.

For each time marker include source evidence, hash the raw artifact (SHA256), and record collector identity, date/time and method of acquisition to maintain chain-of-custody.

Practical commands and collection snippets

Use these commands as quick collection checks. Always save full raw outputs.

# WHOIS / RDAP
whois example.com > whois_example_com.txt
# RDAP (JSON) - registry specific
curl -s "https://rdap.registrar.example/domain/example.com" > rdap_example_com.json

# DNS snapshots
dig +short NS example.com > ns_list.txt
dig @ns1.example.com example.com SOA +noall +answer > soa_example_com.txt
dig example.com ANY +multiline > dns_full_example.txt

# MX / SPF / DKIM checks
dig example.com MX +short > mx_example_com.txt
dig TXT example.com +short > txt_example_com.txt

# TLS certificate via openssl
openssl s_client -connect www.example.com:443 -showcerts /dev/null | openssl x509 -text > cert_example_com.txt

# Capture email headers (save raw .eml from mail client)
  

Evidence preservation & legal readiness

Do not modify systems unnecessarily. For legal admissibility:

• Compute and log cryptographic hashes (SHA256) of all artifacts and media; save originals and working copies.
• Record who collected each artifact, tools used, and the exact UTC timestamps.
• Use a secure storage location with immutable retention where possible (WORM storage or forensics-grade appliance).
• Engage legal counsel early to understand preservation obligations and to prepare law enforcement submissions (FBI IC3, national cyber centers, or local police cyber units).

“Timestamped, hashed artifacts and provider audit logs are the spine of a defensible investigation.”

Common attacker techniques and red flags

• Change primary email or recovery settings at the mail provider, then proceed to request EPP auth codes or registrant email updates at registrars.
• Exploit OAuth consent to get persistent API tokens for registrar/DNS APIs or hosting control panels.
• Use social engineering against registrar support, leveraging look-alike domains or spoofed emails from newly controlled addresses.
• Immediate DNS TTL lowering followed by record swap (A/CNAME/MX) to minimize detection window.

Remediation steps (technical and operational)

1. Regain control of the email account: enforce hardware-backed MFA (FIDO2 keys), revoke suspicious OAuth grants, reset passwords from a known-good device, and check security settings.
2. Contact registrar and DNS provider: request to halt transfers, restore previous WHOIS contact, and revert DNS changes. Provide your logged evidence and open an abuse/incident ticket.
3. Reinstate DNSSEC where supported and rotate API keys for DNS providers and registrars.
4. Issue new TLS certs if old keys may be compromised and revoke suspicious ones using ACME or CA mechanisms.
5. Harden processes: require multi-person approval for registrant changes, enable registrar 2FA and delegated access controls, implement notification-only DMARC monitoring or enforcement depending on risk appetite.

Advanced strategies & future-proofing (2026+)

Prepare for evolving attacker tradecraft with these higher-level defensive moves:

• Adopt zero-trust account recovery workflows: minimize reliance on email-only recovery by using hardware tokens and out-of-band verifications.
• Use registrar-provided abuse APIs and automated monitoring to detect transfer requests and auth code disclosures in real time.
• Invest in DNS history monitoring and CT log alerts integrated into your SIEM to spot unexpected certificates or zone changes within minutes.
• Mandate organizational policies that prevent single-person control of domain and DNS assets — distribute ownership and require notarized or multi-channel validation for critical changes.
• Leverage provider-specific protections: Google Workspace advanced protections for business accounts, registrar locking services, and DNS provider change approvals.

Case example (anonymized)

In late 2025 a mid-market SaaS company reported a sudden loss of email delivery and an unexpected domain transfer attempt. Forensics found an initial Gmail primary-address change (attacker added their recovery email), followed within 3 hours by an EPP transfer request. Correlation of Gmail security logs, registrar ticket history and DNS SOA serials produced a clean timeline: email compromise → OAuth token abuse → registrar auth-code request → DNS TTL reduction → phishing site deployed. Preserving the raw Gmail activity logs and registrar transfer emails enabled rapid registrar intervention and law enforcement engagement; the domain was locked and restored within 72 hours. The client then implemented mandatory FIDO2 for admin accounts and registrar two-person change approvals.

Checklist summary — artifacts to collect

• Raw email message files (.eml) with full headers
• Google Account / Workspace audit exports (login, admin, drive, oauth)
• Registrar WHOIS/RDAP snapshots and transfer request emails
• DNS zone exports, SOA serials, and provider audit logs
• SPF/DKIM/DMARC records and aggregate reports
• Web server and CMS logs, file hashes, and modified file snapshots
• Certificate Transparency entries and ACME/CA issuance logs
• Provider incident ticket IDs and support correspondence
• Hashes (SHA256) and chain-of-custody records for every artifact

Final takeaways

In 2026 the attack vector that starts with an email change and escalates to DNS or registrant compromise is increasingly common. Rapid preservation, methodical collection, and a correlated timeline are the difference between a reversible incident and a catastrophic domain loss. Adopt multi-layered protections (hardware MFA, registrar locks, DNSSEC, and monitoring) and bake forensic logging into your operational playbooks.

Call to action

If you’re facing a live incident or want a readiness audit tailored to your domains, export your critical artifacts and contact sherlock.website for a rapid domain & DNS forensics engagement. We’ll help reconstruct timelines, remediate control loss and advise on legal escalation — with proven 2026 techniques that stop domain attacks before they cost you traffic and trust.

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