Heavy industry is increasingly becoming the target of cyber attackers. Financial institutions may be getting all the press, but industrial networks get more attacks, both in terms of numbers and types of attacks. Many of these seem intended solely to probe for weaknesses—for now. But they represent a serious enough potential to harm U.S. industrial capabilities that the U.S. Department of Homeland Security (DoHS) has now issued recommendations for the protection of industrial control systems.
The DoHS Industrial Control Systems Cyber Emergency Response Team (ICS-CERT) issued in December Seven Steps to Effectively Defend Industrial Control Systems. The document opens by pointing out that the industry reported at least 295 incidents of cyber intrusion to ICS-CERT in fiscal year 2015, with many more likely unreported or undetected. Further, these incidents have been increasing in frequency and sophistication.
Simply building a network with a hardened perimeter (i.e., firewalled) is no longer adequate, ICS-CERT concludes.
To help mitigate against cyberattack, then, the ICS-CERT recommends industrial network owners implement seven key strategies in their networks to improve their defenses. Taking these steps, the agency claims, would have prevented 98% of the incidents reported in FY2015.
The seven key strategies are:
- Implement application whitelisting — By only allowing pre-approved applications to execute, networks can detect and prevent execution of malware. SCADA systems, HMI computers, and database systems are particularly good candidates for this strategy.
- Ensure proper configuration and patch management — Security practices grow stale as adversaries continually improve their capabilities. As a result, unpatched software becomes an increasingly vulnerable target over time. The key is to implement a process for the safe importation and implementation of trusted patches.
- Reduce your attack surface area — Lock down unused ports and turn off unused services. Allow real-time external connectivity only where absolutely needed. And isolate your industrial network from untrusted external networks. A useful tip is if there is only one-way communication needed (i.e., data reporting) use an optical isolation scheme (data diode) to prevent return signals from entering.
- Build a defendable environment — The right structure can help limit potential damage from a perimeter breach. Like a castle with its outer walls and inner fortifications, designing the network as a collection of enclaves with limited host-to-host communications can prevent the compromise of one system from being able to infect others.
- Manage authentication — Stolen credentials can give an attacker virtually undetectable access to key systems. Two-factor authentication, restriction of user privileges to only job-essential access, requiring separate credentials for corporate and control network zones, and a host of other policies are available as mechanisms for reinforcing authentication.
- Secure remote access — If remote access to a network is necessary, take steps to secure it, such as using hardware (not software) data diodes for read-only access, time-limiting remote access, requiring operator control over remote access requests, and avoiding a “double standard” with separate access paths for vendors and employees. Also, find and close any obscure access vectors, hidden back doors, and the like. Especially guard against modems, which are fundamentally unsecure.
- Monitor and respond — Cyberattacks continue to grow in sophistication, so measures that seem adequate today may prove vulnerable tomorrow. Continually monitor networks for evidence of intrusion or other attacks, and have a response plan in place for when attacks are detected. Quick action can limit the damage and facilitate recovery.
More specific techniques for many of these strategies can be found in the document.
Originally posted on Embedded's sister site, EE Times: “Protect industry against cyberattack with these 7 steps.”