Security Checklist for Moving from SaaS Office Suites to Self‑Hosted Solutions

Moving off Microsoft 365 to a self-hosted stack? Start with security — not convenience

Teams are migrating documents and collaboration from SaaS office suites to self-hosted stacks for cost, data sovereignty and control. That move solves some privacy and vendor-dependency problems, but it also transfers operational risk to your team. This checklist focuses on the security controls you must put in place when moving files, mail, calendars and real‑time collaboration off cloud SaaS (e.g., Microsoft 365 / Google Workspace) to solutions like Nextcloud, Collabora/OnlyOffice/LibreOffice and federated chat (Matrix/Element) in 2026.

Quick summary — what to secure first

• Inventory & priority: classify data, export formats, retention and legal holds before moving anything.
• Encryption: transit + at-rest + optional client-side/end-to-end for sensitive docs.
• Backups: immutable, versioned, offsite, regularly tested restores.
• Access controls & identity: central SSO, MFA, RBAC/ABAC, just-in-time privileged access.
• Incident response: logging, SIEM/EDR, playbooks and tabletop drills for migration-stage incidents.
• Supply-chain & governance: software SBOMs, update policies, maintainers and CVE handling.

The 2026 context you must plan for

In 2024–2026 the security and regulatory landscape accelerated three trends relevant to self-hosting:

• Regulators and enterprise buyers demand data sovereignty and audit trails, pushing migrations off multi-national SaaS in sensitive sectors.
• Supply-chain attacks and repo compromise forced adoption of signing and attestation tooling (sigstore, SLSA frameworks) as baseline requirements.
• Cloud outages and geopolitical risk increased appetite for hybrid and multi-site self-hosting to guarantee availability and control.

Pre-migration checklist — don't export until this is done

1. Data inventory & classification:
   • Run a discovery across M365: OneDrive, SharePoint, Exchange, Teams attachments and eDiscovery. Prioritize PII, IP, financial records and regulated data.
   • Label retention and legal-hold records. Use the policy metadata export — you must preserve legal holds and eDiscovery windows.
2. Threat model the migration:
   • Build a concise STRIDE map for the migration phase: what can a malicious insider, compromised tenant admin, or supply-chain attacker do during export and import?
   • Document high-value assets and attack paths and map mitigations (e.g., offline staging, signed export bundles).
3. Define acceptable formats & fidelity:
   • Decide ODF (LibreOffice) vs OOXML conversions and test rendering. Preserve metadata where legal/regulatory needs require it.
   • For mail and calendars, prefer standard formats (EML, MBOX, ICS) and verify attachments and headers are preserved.
4. Export governance:
   • Only allow exports to secure staging hosts with full-disk encryption and monitored network egress.
   • Use time-bound, scoped service accounts for export operations; rotate keys immediately after use.

Encryption: layers you need in 2026

Encryption remains the cornerstone. Cover three layers:

Transport (in transit)

• Enforce TLS 1.3 for all internal & external endpoints. Terminate TLS at your reverse proxy (e.g., NGINX/Envoy) with strict ciphers and HSTS.
• Automate certificate issuance with ACME (Let's Encrypt / internal PKI). Consider mTLS for internal service-to-service calls.

# NGINX TLS example (strict TLS 1.3)
server {
  listen 443 ssl http2;
  ssl_protocols TLSv1.3;
  ssl_prefer_server_ciphers on;
  ssl_ciphers 'TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256';
  # certs via acme client
}
  

At rest (server-side)

• Full-disk encryption (LUKS on Linux) for hosts storing exported bundles.
• Application-layer encryption for data stores: encrypt database fields containing PII using envelope encryption (KMS + data encryption keys).
• Use Hardware Security Modules (HSMs) or cloud KMS for key management when available; for on-prem, use StrongHSM or Vault.

# Example: create an encrypted LUKS partition
sudo cryptsetup luksFormat /dev/sdb1
sudo cryptsetup open /dev/sdb1 secure-data
sudo mkfs.ext4 /dev/mapper/secure-data
  

Client-side / End-to-end

For extremely sensitive documents, implement client-side encryption before upload. Tools and patterns in 2026:

• Use age or GPG for document envelopes. Provide user-friendly integration for non-technical users during migration.
• For collaboration, consider end-to-end encrypted messaging (Matrix with Megolm for group chat) and E2EE-enabled file sharing plugins.

# Encrypt a file with age
age -o secret.txt.age -r recipient_public_key secret.txt
  

Backups: design for immutability and fast recovery

Backup and restore are the most common gaps teams find after migration. You need a robust, testable strategy.

Requirements

• Immutable, versioned backups: prevent silent deletion or ransomware encryption of backups.
• Geographically separated copies: at least one copy offsite and another in a different availability zone/colocation.
• Regular restore tests: quarterly or monthly depending on SLAs, with documented RTO/RPO targets.

Tooling examples

• restic (with S3-compatible backend + object lock) or Borg/Attic for deduplicated snapshots.
• rclone for large data migrations and cross-backend copies.

# restic backup to S3-compatible with object lock enabled
export AWS_ACCESS_KEY_ID=...
export AWS_SECRET_ACCESS_KEY=...
restic -r s3:s3.example.com/nextcloud-repo backup /var/www/nextcloud/data
  

Practical backup checklist

• Enable object locking / WORM on S3 buckets used for backups.
• Keep at least 90 days of granular versions and a yearly archive for compliance.
• Automate restores to staging environments and validate file integrity and metadata preservation.

Access control & identity

Centralize identity and enforce least privilege across services and plugins.

Authentication & federation

• Use enterprise SSO (SAML/OIDC) via Keycloak, Dex or your IdP. Avoid local accounts for admin tasks.
• Enforce strong MFA policies for admin and privileged users. Consider phishing-resistant methods (FIDO2/WebAuthn).

Authorization

• Apply RBAC for teams and ABAC for resource-specific conditions (e.g., docs marked confidential may be read-only outside certain IPs).
• Use just-in-time (JIT) elevation for privileged operations; log and require approval for long-lived admin roles.

Least-privilege checklist

• Remove default admin accounts or rotate their credentials; apply unique identities for automation scripts.
• Audit third-party integrations (Collabora, OnlyOffice connectors) and run them with minimal scopes.
• Enforce session timeouts and device posture checks for remote access.

Secure migration operations — technical patterns

Below are repeatable, practical steps to migrate content while containing risk.

Staged exports — isolation + verification

1. Export data to an isolated staging host with full-disk encryption and EDR monitoring.
2. Compute and sign checksums (SHA-256) for bundles. Store signatures in a separate, immutable location.
3. Perform integrity checks before and after import.

Migration command examples

# rclone copy from SharePoint to S3-compatible storage
rclone copy "sharepoint:site/docs" s3:staging-exports/site-docs --transfers=8 --exclude "*.tmp"

# create sha256 and sign with gpg
sha256sum export.tar.gz > export.sha256
gpg --detach-sign export.sha256
  

Minimize blast radius

• Do large migrations out of business hours with notification and rollback options.
• Limit network egress to required destinations via firewall rules during migration windows.

Incident response: plan for migration-specific failures

Migration introduces transient risk: leaked credentials, malformed imports, or accidental public exposure. Build playbooks tailored to these risks.

Essential playbook elements

• Immediate containment steps: revoke tokens used for export, rotate service account credentials, and isolate affected hosts.
• Evidence preservation: snapshot VMs, collect logs, and secure exported bundles' checksums and signatures.
• Notification matrix: legal, data protection officer, executives, affected users and regulators (if required by law).
• Recovery actions: failback plan to source SaaS or last-known-good backup with documented rollback steps.

Logging & detection

• Centralize logs for authentication, file access, and admin actions in a SIEM (Elastic/Splunk/QRadar) with retention set per compliance needs.
• Use EDR on hosts performing migration; monitor for unusual process activity or network connections to unknown C2 domains.
• Enable file integrity monitoring on critical mounts (AIDE, osquery).

Governance, licensing & compliance

Self-hosting introduces licensing and governance tradeoffs. Document them before moving.

Open-source license checklist

• Inventory the stack (Nextcloud, Collabora, LibreOffice, Matrix, PostgreSQL, etc.) and record licenses (AGPL, MPL, LGPL, MIT).
• Understand obligations: some server-side copyleft (AGPL) requires offering source if you provide networked service; plan legal review for public-facing deployments.
• Manage contributor license agreements or DCO processes if you plan to contribute back.

Compliance and data protection

• Map data flows and maintain a records register. Ensure exports preserve required audit trails for GDPR, HIPAA or other regulations.
• If subject to breach notification laws, include migration scenarios in your breach-notification timeline and evidence requirements.
• For regulated environments consider obtaining SOC2/ISO27001 certification for the self-hosted operational practices, not necessarily the software itself.

Supply chain, updates and maintaining security posture

Self-hosting means you’re now responsible for timely updates and supply-chain hygiene.

• Adopt signed releases and verify signatures. Prefer repositories supporting sigstore or package signing.
• Generate SBOMs for deployed components and track CVEs in a vuln management system (e.g., Dependabot, OSV, private scanner).
• Automate patching for non-disruptive components and schedule maintenance windows for major upgrades with rollback plans.

Operational security: runbooks and team responsibilities

Define ownership — who runs backups, who is on-call for restores, who approves exports?

• Create short runbooks for: export operations, importing document sets, verifying conversions, and emergency rollback.
• Train admin teams on cryptographic key rotation, vault recovery, and secure secret injection in CI/CD.
• Run tabletop exercises simulating a compromised export key or a failed migration restore.

Practical migration timeline & priorities

Example phased approach (6–12 weeks for a medium-sized team):

1. Week 0–2: Inventory, threat model, choose stack and test exporters.
2. Week 3–4: Build staging environment (SSO, TLS, disk encryption), and perform small pilot export + import for a single team.
3. Week 5–8: Scale migration in waves, validate backups & restores, and run IR tabletop exercise.
4. Week 9–12: Decommission SaaS endpoints, finalize retention and compliance artifacts, and publish post-migration runbooks.

Examples & quick wins

• Use Nextcloud + Collabora for collaborative docs with server-side encryption, and add client-side age encryption for extremely sensitive files.
• Replace Exchange with a well-configured Postfix/Dovecot cluster or a managed mailhost — ensure full TLS and DKIM/SPF/DMARC alignment before cutover.
• For chat, deploy Matrix with E2EE enabled for private rooms and integrate SSO for account management.

Common mistakes to avoid

• Skipping restore testing. Backups are worthless until you can reliably restore and verify integrity.
• Assuming open-source equals secure. Track CVEs, configure defaults, and harden the stack.
• Exporting everything at once. Use waves to reduce blast radius and allow time for conversion fixes.
• Neglecting legal holds and retention. Exports must preserve legal metadata where required.

Security isn't a feature you enable at cutover — it's an operational discipline you run continuously.

Actionable 10-point migration security checklist (printable)

1. Complete data inventory & classify sensitivity and legal-hold items.
2. Threat model migration and document mitigations.
3. Stage exports on encrypted, monitored hosts; use scoped service accounts.
4. Sign and checksum export bundles; store signatures separately and immutably.
5. Enforce TLS 1.3 + mTLS where applicable; automate cert issuance.
6. Encrypt at rest (LUKS + application envelope encryption) and use HSM/KMS for keys.
7. Implement versioned, immutable backups (S3 object lock + restic/Borg) and test restores.
8. Centralize identity with SSO, enforce MFA and RBAC/JIT privilege elevation.
9. Enable logging, SIEM alerts, and EDR on migration hosts; document IR playbooks and run drills.
10. Maintain SBOMs, verify signed releases, and schedule timely security updates.

Final notes: when self-hosting makes sense — and when it doesn't

Self-hosting gives control and can improve privacy and resilience when properly executed. But it also requires operational maturity: people, processes and tooling. If you cannot commit to the checklist above, consider hybrid approaches — keep mail in managed SaaS while self-hosting documents, or use managed self-hosted offerings that handle patching and backups.

Next steps & resources

• Run a 2-week pilot with one team and validate conversions, backups and IR playbooks.
• Build SBOMs and adopt sigstore to verify third-party binaries and container images.
• Document compliance mapping (GDPR/HIPAA/SOC2) for the new stack and schedule audit evidence collection.

Call to action

If you're planning a migration from Microsoft 365 this year, take the checklist above and run a pilot in the next 30 days. Need a one-page export checklist or a sample playbook for breach response during migration? Download our free Migration Security Playbook and get a starter set of scripts for rclone/restic + sample Keycloak SSO configs tailored for self-hosted office stacks.

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