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Introduction:
The 2021 Oldsmar, Florida water treatment hack wasn’t just a story about a compromised utility; it was a stark revelation of how fragile Industrial Control System (ICS) security truly is. When an attacker gained remote access and attempted to poison the water supply by manipulating sodium hydroxide levels, the industry learned that the real vulnerability wasn’t just the internet connection—it was the very architecture of remote operations. In Operational Technology (OT) environments, where safety and process continuity are paramount, remote access solutions often merge with daily engineering workstations, creating a privileged conduit that turns maintenance tools into weapons.
Learning Objectives:
- Understand the attack vectors exposed by the Oldsmar incident and how remote access flaws are exploited in ICS environments.
- Learn to apply the IEC 62443 standard to architect secure remote access zones and conduits.
- Gain practical skills in implementing Multi-Factor Authentication (MFA), Just-in-Time (JIT) access, and session monitoring for industrial networks.
You Should Know:
- The Anatomy of the Oldsmar Attack and the “Always-On” VPN Problem
The Oldsmar attack succeeded not because of sophisticated malware, but because of poor remote access hygiene. Attackers likely gained entry through a VPN that lacked MFA, combined with shared passwords on a Human-Machine Interface (HMI). Once inside, they had the same level of access as a legitimate operator because the remote path landed directly on the workstation used for daily control.
Step‑by‑step guide: Auditing VPN and Remote Desktop Protocols in OT
To prevent this, you must first audit your current exposure. Here’s how to check for open RDP and VPN gateways from an external and internal perspective.
Linux Command (External Scan):
Use `nmap` to identify exposed remote services on your OT perimeter. Note: Only scan assets you own or have explicit permission to test.
Scan for common VPN ports (IPsec: 500/4500, OpenVPN: 1194, PPTP: 1723) and RDP (3389) nmap -sS -p 500,4500,1194,1723,3389 -Pn <OT_Gateway_IP_Range>
Windows Command (Internal Audit):
Check for listening services on engineering workstations to ensure RDP isn’t inadvertently enabled for external access.
Check if RDP is listening on a Windows Engineering Workstation Get-NetTCPConnection -LocalPort 3389 -ErrorAction SilentlyContinue Check the firewall rule for RDP Get-NetFirewallRule -DisplayName "Remote Desktop" | Get-NetFirewallAddressFilter
If RDP is open to the world or listening on a domain profile that connects externally, you have an Oldsmar-style risk.
2. Implementing the IEC 62443 “Conduit” Model
IEC 62443 dictates that communication between zones (e.g., the Corporate Network and the Control Center) must occur through a defined “conduit” that enforces security policies. Instead of placing a vendor directly into the control zone, you create a managed jump host or Privileged Access Management (PAM) solution.
Step‑by‑step guide: Setting up a Linux Bastion Host as an OT Conduit
This bastion host acts as the single choke point for all remote engineering access.
Linux Configuration (Bastion Host Setup):
Update the system and install necessary tools sudo apt update && sudo apt upgrade -y sudo apt install openssh-server auditd fail2ban -y Harden SSH configuration (edit /etc/ssh/sshd_config) Disable root login, use key-based auth, and change default port sudo sed -i 's/PermitRootLogin yes/PermitRootLogin no/' /etc/ssh/sshd_config sudo sed -i 's/PasswordAuthentication yes/PasswordAuthentication no/' /etc/ssh/sshd_config sudo systemctl restart sshd Configure auditd to log all commands executed on the bastion sudo auditctl -w /var/log/auth.log -p wa -k ssh_logs sudo auditctl -w /home/ -p wa -k user_activity
All vendors must now SSH into this bastion first, and from there, access the HMI or PLC network via a controlled RDP or native OT protocol tunnel. This ensures all actions are logged and attributable.
3. Hardening Engineering Workstations with Just-in-Time (JIT) Access
The Oldsmar attacker used an already-authenticated session. JIT access ensures that privileges are temporary and must be requested and approved for each specific task.
Step‑by‑step guide: Implementing JIT with PowerShell for Windows Engineering Stations
This script elevates a standard user to an administrator group for a limited time, with logging.
Windows PowerShell (Admin) – JIT Elevation Script:
Run this on the Engineering Workstation or Domain Controller param( [bash]$EngineerName, [bash]$ValidHours = 2 ) $EndTime = (Get-Date).AddHours($ValidHours) $LogFile = "C:\OT_Security\JIT_Audit.log" Add user to local admin group (or a specific OT-Engineering group) Add-LocalGroupMember -Group "Administrators" -Member $EngineerName -ErrorAction SilentlyContinue Log the action "$((Get-Date).ToString()): JIT Admin access granted to $EngineerName until $EndTime" | Out-File $LogFile -Append Schedule a job to remove the user after time expires $Action = New-ScheduledTaskAction -Execute "powershell.exe" -Argument "-Command Remove-LocalGroupMember -Group 'Administrators' -Member '$EngineerName'; Write-Output 'Access Removed' >> $LogFile" $Trigger = New-ScheduledTaskTrigger -Once -At $EndTime $Principal = New-ScheduledTaskPrincipal -UserId "SYSTEM" -LogonType ServiceAccount $Settings = New-ScheduledTaskSettingsSet Register-ScheduledTask -TaskName "Revoke_JIT_$EngineerName" -Action $Action -Trigger $Trigger -Principal $Principal -Settings $Settings
4. Session Recording and Real-Time Alerts
You cannot secure what you cannot see. In OT, malware is not the only threat; malicious engineering changes are equally dangerous. Session recording provides a visual playback of exactly what a vendor or operator did.
Step‑by‑step guide: Using `script` and `tlog` for Linux Session Recording
If your bastion host is Linux, you can force session recording for all users.
Linux Configuration (Bastion Host):
Add the following to the `.bashrc` or use a system-wide profile to start a recording session upon login.
Add to /etc/profile.d/session_log.sh This starts a script recording for every SSH session LOG_DIR="/var/log/ot_sessions" if [ ! -d "$LOG_DIR" ]; then sudo mkdir -p "$LOG_DIR" sudo chmod 755 "$LOG_DIR" fi LOG_FILE="$LOG_DIR/session_$(date +%Y%m%d_%H%M%S)_$USER.log" Start script command to record the session silently script -q -f "$LOG_FILE" exit
This forces every command typed during the remote session to be saved to a log file. For Windows RDP sessions, tools like `Terminal Services Session Recording` or third-party PAM solutions are required.
5. Detecting Anomalous Engineering Changes
Beyond recording, you need to detect the change itself. In Oldsmar, the mouse moved on its own and the setpoint changed. In a network, this looks like a protocol anomaly.
Step‑by‑step guide: Monitoring Modbus Traffic with Tcpdump
If the attacker had manipulated a setpoint, the Modbus write command would have been visible. Here’s how to capture industrial protocol traffic to establish a baseline.
Linux Command (Network Monitoring):
Place a machine with port mirroring (SPAN port) on the OT switch.
Capture Modbus/TCP traffic (port 502) and look for write commands (Function Code 16 or 6) sudo tcpdump -i eth0 -n port 502 -A -c 1000 To specifically filter for Modbus write requests to a holding register This requires deeper inspection; using tshark is better tshark -i eth0 -Y "modbus.func_code == 16 || modbus.func_code == 6" -T fields -e ip.src -e modbus.regnum -e modbus.value
In a healthy environment, writes should correlate with scheduled maintenance windows. If a write occurs at 02:00 AM with no ticket, it is a potential Oldsmar-style incident.
What Undercode Say:
- Key Takeaway 1: Remote Access is a Process Safety Risk. The Oldsmar incident proves that cybersecurity in OT is not just about data confidentiality; it is about physical safety. Securing the “engineering path” is as critical as securing the chemical reaction itself. Treat remote access with the same rigor as a safety instrumented function.
- Key Takeaway 2: Visibility Trumps Prevention. While firewalls and VPNs are necessary, they failed at Oldsmar. The real defense lies in visibility—knowing who changed what, when, and being able to prove it within an hour. Without session recording and change alerts, you are blind to the insider or the compromised vendor.
The convergence of IT security tools (like MFA and PAM) with OT process knowledge is the only way forward. Utilities and critical infrastructure operators must move beyond compliance and start designing their networks to assume that the vendor’s connection is already compromised, forcing every action to be verifiable and reversible.
Prediction:
The next major infrastructure hack will not rely on zero-day exploits in PLC firmware. Instead, it will abuse the maintenance features designed to keep plants running. As OT environments become more connected, regulators will mandate “Digital Safety” protocols, similar to IEC 61511, where remote engineering commands require a two-person rule or a hardware key turn, effectively baking cybersecurity into the physical safety lifecycle. We will see a future where every remote logic change requires a cryptographic signature verified by the PLC itself, rendering stolen credentials useless for process manipulation.
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Reported By: Antonio Gonzalez – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
