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Introduction:
In Operational Technology (OT) environments, where uptime is critical and safety systems are non-negotiable, the most overlooked cybersecurity control is often the simplest: backup and recovery. Unlike IT environments where data integrity is the primary focus, OT demands rapid restoration of industrial processes to prevent physical damage and production downtime. As highlighted by an upcoming webinar from Macrium and Mike Holcomb, organizations are frequently overconfident in their ability to recover from a ransomware attack or system failure, only to discover gaps in their recovery program when it is too late.
Learning Objectives:
- Understand why backup and recovery is considered the 1 cybersecurity control in OT/ICS environments.
- Identify the key differences between IT disaster recovery and OT operational resilience.
- Learn how to implement and test a verified backup strategy using native OS tools and third-party solutions.
You Should Know:
- Verifying Your OT Recovery Plan: Beyond the “Checkbox” Backup
Most organizations believe they are prepared for an incident until they attempt a full system restore in a time-critical scenario. A recovery program is not just about having backups; it is about proving they work under pressure. In OT environments, this means validating that backups include not just data, but also the specific configurations of PLCs, HMIs, and network switches that define the operational process.
To start verifying your preparedness, begin by auditing your current backup strategy. Use the following commands on Windows-based engineering workstations or HMI servers to check backup logs and shadow copies, which are often the first line of defense against accidental deletion or encryption.
Windows (Check VSS Writers and Backup History):
vssadmin list writers wmic /namespace:\root\microsoft\windows\backup path win32_backupjob get /format:list
Linux (Check Cron Jobs and Rsync Logs):
sudo grep -i "rsync|backup" /var/log/syslog | tail -20 sudo systemctl list-timers --all | grep -i backup
Step‑by‑step guide to auditing your OT recovery plan:
- Inventory Critical Assets: List all PLCs, RTUs, HMIs, and historians. Identify which devices have configuration backups stored off-device.
- Map Recovery Dependencies: Determine the boot order. Does the HMI require the historian to be restored first? Document the sequence.
- Test a Blind Restore: Take one non-production HMI or engineering workstation. Perform a full system restore from backup without looking at the “standard operating procedure” to see if the documentation is actually usable.
- Measure Time to Recover (TTR): Record how long it takes from initiating the restore to having the system functionally operational. Compare this against your Recovery Time Objective (RTO).
2. Implementing Immutable Backups for Ransomware Resilience
In the context of OT security, ransomware is a top threat because it can lead to physical process manipulation or shutdowns. Immutable backups—backups that cannot be altered, encrypted, or deleted—are essential. The “3-2-1” backup rule (three copies, two media types, one off-site) is the minimum standard, but for OT, a “3-2-1-1-0” rule is better: 3 copies, 2 media, 1 off-site, 1 immutable, and 0 errors.
To harden your backup infrastructure against attackers who may move laterally from IT to OT, configure your backup repositories to require multi-factor authentication and isolate them from the main domain.
Example: Configuring a Linux-based Immutable Repository using `chattr`
On a hardened Linux backup server, you can set the immutable flag on backup directories to prevent deletion or modification, even by the root user if the system is compromised.
Assuming backup directory is /mnt/backups/ot_assets sudo chattr +i /mnt/backups/ot_assets Verify the attribute lsattr /mnt/backups/ | grep ot_assets
Note: To modify or delete files here later, you must remove the flag with sudo chattr -i.
Windows: Configuring Volume Shadow Copy for Rapid Recovery
For Windows-based OT systems (like SCADA servers), Volume Shadow Copy (VSS) allows for rapid restoration of previous file versions.
List current shadow copy storage space vssadmin list shadowstorage Configure a larger storage area for shadow copies (e.g., 20% of volume) vssadmin resize shadowstorage /for=C: /on=C: /maxsize=20% Create a manual shadow copy (for testing) vssadmin create shadow /for=C:
- The Role of Cloud and Off-Site Air-Gapped Strategies
While air-gapped networks are a staple in OT philosophy, modern hybrid architectures often require cloud-based or off-site recovery solutions. The webinar emphasizes that recovery “doesn’t have to be hard,” which implies leveraging modern tools that support encrypted, off-site backups without compromising the air gap. If your OT network cannot connect directly to the cloud, consider a “sneaker-net” approach using encrypted external drives rotated manually, or a one-way data diode solution that allows metadata to flow out while preventing inbound threats.
Step‑by‑step guide to implementing a secure off-site sync:
- Encrypt Before Transport: Ensure backups are encrypted using AES-256 before they leave the OT network. Use tools like `gpg` on Linux or `BitLocker` on Windows for external drives.
- Use a Bastion Host: If transferring to the cloud, use a dedicated bastion host that sits in a DMZ between the OT network and the cloud. This host should have no direct inbound access from the internet.
- Automate with SSH Keys (Linux): For secure transfers to a remote server or cloud storage, use SSH key authentication without passwords to prevent brute-force attacks.
Generate an SSH key on the backup server ssh-keygen -t ed25519 -f ~/.ssh/ot_backup_key -N "" Copy the public key to the remote server ssh-copy-id -i ~/.ssh/ot_backup_key.pub [email protected]
- Verify Integrity: Always create and verify checksums after transfer to ensure data integrity in the air-gapped environment.
sha256sum critical_plc_config.bin > checksums.txt sha256sum -c checksums.txt
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Automating Recovery Drills with CI/CD for OT Configurations
Modern OT security is moving toward “as-code” configurations, allowing for faster recovery. By storing PLC configurations, HMI screens, and network device configs in version control systems (like Git), you can automate the recovery process. While you cannot fully automate a PLC flash remotely without safety interlocks, you can automate the deployment of virtualized HMIs and historians.
To test your recovery speed, set up a simple script that simulates a restore of a critical configuration file from a Git repository.
Example: Restoring a PLC Configuration from Git (Simulated)
Clone the repository containing device configurations git clone https://git.internal/ot/configs.git /tmp/restore_test Verify the specific version needed (e.g., the last known good config) cd /tmp/restore_test git log --oneline | head -5 Checkout the specific commit for the PLC git checkout [bash] -- ./plcs/water_treatment_ladder.xml
5. Hardening Windows and Linux Backup Agents
Backup agents themselves are a potential attack vector. If an attacker compromises the backup software, they can disable protection or exfiltrate data. Ensure that the service accounts running backups follow the principle of least privilege.
Windows: Configure a Managed Service Account (MSA) for Backup Services
Create a Group Managed Service Account (requires Active Directory) New-ADServiceAccount -Name BackupSvc -DNSHostName backup.domain.com Install on the backup server Install-ADServiceAccount -Identity BackupSvc
Linux: Harden `rsync` Daemon Permissions
Edit `/etc/rsyncd.conf` to restrict access to specific modules and IPs.
[bash] path = /var/backups/ot comment = OT Secure Backup hosts allow = 192.168.1.0/24 read only = no auth users = backup_user secrets file = /etc/rsyncd.secrets
What Undercode Say:
- Overconfidence is a vulnerability: The premise of the webinar is critical—assuming you are ready without rigorous, scheduled recovery tests leads to catastrophic failures during an actual incident. OT environments cannot afford the “learning curve” of a restore during an outage.
- Isolation is not enough: While air-gapping is foundational, it does not protect against insider threats or physical media corruption. Combining immutable backups with frequent integrity checks ensures that when you need to recover, the data is both safe and functional.
- Automation bridges the gap: The gap between IT and OT recovery is closing. By applying IT principles like version control (Git) and immutable infrastructure to OT assets, security teams can drastically reduce Mean Time to Recover (MTTR).
Prediction:
The next wave of OT ransomware attacks will not focus on encrypting live systems but on corrupting or deleting backups before the payload deploys. This shift will force organizations to prioritize immutable, offline, and frequently tested backup strategies as the primary defense mechanism. As the March 25th webinar suggests, the distinction between IT and OT recovery will blur, leading to unified disaster recovery frameworks that treat industrial safety as the ultimate data integrity metric.
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