As we read or hear about industrial control system (ICS) security, the focus is often placed on ‘cyber’ protection measures. However, a true security program for ICS and supporting systems should be a holistic to ensure integration of both cyber security and physical security measures. Unfortunately, physical security tends to be ignored in too many instances.
Cyber security standard; ISA/IEC-62443-2-1, Security for Industrial Automation and Control Systems, includes a section on Physical and Environmental Security. The two subsections are focused on Secure Areas (11.1) and Equipment (11.2).
The objective of Physical and Environmental Security is “To prevent unauthorized physical access, damage and interference to the organization’s information and information processing facilities.” Essentially a key aspect of this standard is to implement effective access control and protection of systems and equipment from damage.
Physical Security Perimeter (PSP)
One of the first actions an ICS security review should include is identification and verification of the physical security perimeter(s) surrounding the Industrial Control Systems. With this perimeter, physical access points (e.g. entry/exit points) should be identified. These perimeter barriers should be physically sound with no gaps or weak points where break ins could easily occur. Additionally, consideration should be given to the ‘6-sided-barrier’concept of ceiling, floor and four walls.
All external doors or gates to the perimeter should be protected against unauthorized access with control mechanisms such as locks, CCTV, alarms, etc. Doors and windows should be locked when unattended and ground-level windows need extra protection such as bars, metal mesh, for example.
As a reminder, the defence in depth concept also applies to the PSP. It is satisfactory and even necessary to have multiple layers of physical protection around systems – especially those which perform sensitive functions where intellectual property and proprietary operations are stored and occur respectively.
Although the PSP is in place to keep intruders and outsiders from accessing the ICS systems and information, access controls also need to be in place for approved personnel, vendors and escorted visitors.
The following access controls should be considered:
- A physical log book or electronic audit trail of all access, along with date and time of PSP entry/exit, should be securely maintained, stored and monitored;
- All visitors must be escorted and supervised when inside the PSP;
- Access to areas containing confidential/proprietary information should be restricted to authorised individuals and only via strong access controls such as an access card and PIN;
- All employees, contractors, third-party vendors, and/or visitors inside the PSP should wear some form of visible identification;
- Access rights to secure areas should be regularly reviewed and updated (recommended monthly), and unnecessary access permissions should be revoked.
Equipment Siting and Protection
Industrial Control Systems and information should be protected from damage, loss, theft or compromise. Some key considerations in this domain include:
- Fire detection/protection systems should be installed and activate automatically in the event of a fire;
- Temperature and humidity should be maintained within acceptable levels – especially for servers and workstations;
- ICS should be protected from water damage due to broken plumbing lines, HVAC drains, etc.;
- Lightning protection and effective grounding should be applied to all buildings housing ICS;
- Loss of key utility services can disable an operating environment very quickly. Such disruptions should be analysed and protected against by considering some of the following techniques:
- Power and telecommunications infrastructure should be protected from interception, interference or damage (e.g. backhoe cuts or sabotage);
- Electric service, telecommunications, internet, etc. should be provided by means of primary and secondary feeds for large or critical facilities. These feeds should be geographically separated and originate from separate sources if possible. Consider having the feeds at opposite ends of the facility.
- Provide short-term uninterruptible power supplies (UPS) to facilitate an orderly shutdown of the ICS in the event of a primary power source loss;
- Emergency lighting should be in place that activates in the event of a power outage and covers emergency exits and evacuation routes.
Secure Disposal or Reuse of Equipment
As part of systems lifecycle, servers, workstations or ICS components are marked for disposal or reuse. In these instances, it is critically important that all equipment containing storage media (e.g., hard drives) is sanitised to ensure any sensitive data and licensed software has been removed and securely overwritten (or physically destroyed) prior to disposal or reuse.
Staying on Top of Physical Security is a Full-Time Job
The list of physical security parameters above is not complete but will give you a sense of the scope and depth of what needs to be addressed. Treating physical security as a part-time job is simply not effective and will often result in more crises rather than improved security.
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