reduce ransomware risk in OT/ICS

5 Ways to Reduce Ransomware Risk for OT/ICS

Enhancing these five categories reduces the risk of a ransomware infection, leverages existing technology investments and improves recovery.
Ron Brash

Cyber security has gone through the paces by attackers, and we will continue to see permutations of older malicious techniques and the addition of new threats or strategies as it evolves further. Whether for extortion of money, disruption, or even as a vector to hide one’s tracks, ransomware is a very painful experience for the victim of a successful attack. Just ask Maersk, Mondelez and Honda.

As with every security risk or threat, it needs to be understood, clarified, deconstructed, and mitigated. The purpose of this blog is to answer these common questions about ransomware

  • What is ransomware?
  • How does ransomware work?
  • Why is ransomware used and what are the potential impacts?
  • How does ransomware affect operating technology (OT) specifically?
  • What you can do to minimize the risk and impact of ransomware?

Now without the doom and gloom, or hacker in hoodie cyber security scare tactics, onwards we go.


What is ransomware?

Ransomware is a type of malicious software that isn’t easy to label as one single type of malware due to it possessing multiple attributes (e.g., a worm or virus), but rather by it’s objective: to make systems unusable through encryption, spread, and to extort money/cryptocurrency for the cure or even to blackmail the victim to prevent the disclosure of sensitive data.

In many cases, ransomware is not strategic in its target selection, it’s indifferent to whom it targets, and it can be very opportunistic. Think of it as a group of criminals: they usually prey on the weak, and their victims are often forced to pay a protection fee or suffer the consequences.

In some cases, ransomware is used by more focused adversarial groups to target a specific organization and cause large-scale disruptions or costly downtimes.

Ransomware malware families timeline exampleFigure 1: Ransomware malware families example timeline


It is important to note that ransomware is not new (e.g., AIDS trojan scam in 1989), but the increased preference of use by attackers as an easy way to scam large audiences is a growing concern. Between 2017 and 2018, ransomware usage grew over 229%, and unfortunately, it is a risk that is here to stay.


How does ransomware work?

Ransomware is not a single tool that has a single function. In fact, it has several components that take advantage of multiple vulnerabilities in a system or organization, exploits them, then proceeds to encrypt files rendering a system unusable while requesting payment, and even looks for further vulnerable hosts to attack. These components are generally a: dropper, encrypter, and decryptor.

Example of ransomware functionality

Figure 2: Simplified example of ransomware function


Generally speaking, ransomware finds its way into a vulnerable system, compromises it (via the dropper), then activates other worm-like functionality to raise the numbers of infected systems while encrypting files (the encryptor), and then waits for payment/decryption (decryptor). The more systems infected, the higher the impact on the victim, and the more likely the “ransom” will be paid.

In other cases, more criminal-driven actors manage to get privileged access to infrastructure such as an Active Directory (AD) server and use management channels to distribute group policy objects (GPO) that install ransomware on the managed systems.

Obviously, privileged access requires more hands-on activity by the actor, but it causes greater levels of impacts that might increase the likelihood of payment or sheer economic disruption for a nation-state target.


Why is ransomware used and what are the potential impacts?

Ransomware has roots in the scam and extortion criminal world, but by nature, it can also be used to target larger asset owners and organizations or to mask other activities that might be more devious.

Let’s first look at why ransomware is so prevalent today:

  • Most ransomware takes advantage of older vulnerabilities that have been left unpatched. When there is a huge supply of commodity exploits, there is little need to create new ones.
  • Ransomware often exploits network-based insecurities to gain access (e.g., through RDP), but spreads from endpoint to endpoint. Compensating controls, system hardening, vulnerability management and other techniques such as network isolation all play a critical role in reducing the impact and spread of an attack.
  • Ransomware is often very effective because many organizations are insufficiently protected. Companies that are not protected have non-existent or incomplete backups, little capability to restore quickly, and inadequate endpoint protection to prevent commodity malware or attacks. This is even more true on legacy systems as commonly seen in industrial and operating technology environments
  • Sometimes payment is required to restore operations (despite principle) because the organization is GREATLY unprepared for an attack despite decades of well-understood best practices.
  • Humans are often unknowingly participants in the attack. They regularly fall for phishing scams, so email or clicking attachments/downloads presents a great (and easy) way to compromise an organization.
  • The Internet and services stacked upon it (e.g., the Internet, or remote access) raise the ease of selecting a target. The economics of this type of attack are in the favor of the attacker.

Of course, there are other aspects that make ransomware attacks so prevalent such as the nature of crypto currency, but the key thing to keep in mind is that they often exploit:

  • Phishing, and downloads
  • Leverage older vulnerabilities that often have patches or compensating options
  • Holes in network security (exposed systems or services)
  • Adjacent networked hosts and segments
  • Lack of validated backups and poor restorative processes


Figure 3: The stereotypical ransomware scenario from IT to OT

In the traditional enterprise Informational Technology (IT) world, ransomware is especially devastating when trying to keep businesses operating with tight dependencies on data and transactions. This ranges from denying access to a paid service, accounts payable, email, or more.

On the other hand, in Operational Technology (OT) or critical infrastructure environments (especially where there are IT systems providing OT services, or an organization that has both IT and OT), ransomware lays waste to swaths of poorly protected systems or results in collateral damage (e.g., encryption and loss of utility of an HMI would render a loss of visibility event, that would result in either manual control, or a complete shutdown of the process that it was monitoring).

So far to date, few, if any, ransomware attacks specifically targeted OT systems, but rather targeted organizations that had OT systems, and relied on IT to provide OT the means to operate/generate revenue.


How does ransomware affect OT specifically?

In OT, regardless if OT is specifically a target of ransomware (which so far has stuck to traditional commodity IT systems such as Windows, Linux, or Apple/Macs), the potential impacts might be as follows:

  • Windows-based infrastructure is compromised, and functionality is denied (e.g., no file servers, no AD, no HMIs, etc.)
  • Infrastructure that is greatly dependent on information feeds such as orders or logistics are often based on data, but drive OT production. Without a suitable alternative (e.g., paper), product may be halted, or be unable to be shipped.
  • Disclosure of trade or process secrets may be a consequence from a ransomware extortion (paid or not!)
  • Costs to recovery ARE IN ADDITION to the costs of disruption. In other words, the cost to return to business as usual may be magnitudes greater than intended because it's not just be the restoration of computers, but the shutdown and revalidation of the process itself (e.g., integrity testing of a section of pressurized pipe when brought back online). This leads to additional closures due to additional faults being discovered or complications in your scheduled maintenance cycles.
  • Business shutdown, divestment, and/or bankruptcy. In industries that are high-volume low-margin, or high-burn (e.g., hourly shutdown cost can easily outpace profits or contingency reserves), a high-impact ransomware attack may be the siren’s song signaling the permanent shutdown of a site (or organization). This has huge consequences.
  • And it has to be said, there may be damage to an organization's reputation, legislative/compliance costs, and a number of other consequences. For example, if a lack of controls are found, cyber insurance may be revoked, or be entirely unavailable.


What you can do to minimize the risk and impact of ransomware?

I promised that this article would not be all doom and gloom, despite the technical and in-your-face risks. Ransomware is a challenging adversary, but it can also be similar to managing other cyber-enabled threats.

In fact, many of those IT-based technologies or strategies work in OT, provide improved return on investment (ROI) and could even be more effective due to the nature of OT; it’s often steady state, isolated, or, overly cautious.

However, overly cautious organizations that aim for a passive-only approach (e.g., passive network monitoring or scanning) must realize that by the time you detect ransomware on a network and receive an alarm, it's too late. Other controls relating to prevention, reaction, and recovery have a larger impact on reducing ransomware risk and impact.

So, what can you do? Well, unfortunately, the reality is – you cannot entirely eliminate the risk, but you can reduce the risks/impacts to more tolerable levels.


Reduce ransomware risk in 5 areas:

  • Endpoint Management
    • Asset inventory: Effective endpoint management begins with a robust asset inventory. As the age old saying goes, if you don’t know what you don’t have, you can’t manage the risks. A rich view of a 360-degree picture of each endpoint enables proper endpoint management.
    • OT systems management: But OT asset inventory is only the beginning of a robust endpoint management program. A robust OT Systems Management program includes configuration hardening, user and account management, software management, etc. In many cases, OT systems are insecurely designed and unpatched, making it ripe for ransomware.
    • Patch management: Most threats enter through commodity systems such as Windows machines. You cannot patch everything in OT, but an end-to-end patch management program (i.e. automation and intelligent application of patches) is of great importance due to several environmental factors such as compliance, legislation, and risk management (e.g., patches on hosts with RDP or firewalls connected to the Internet should be prioritized over a PLC protected by several layers). Where unfeasible, application whitelisting and policy enforcement makes an attacker’s life very difficult improving your chances to defend or deny a ransomware attack.
    • Removable media: USBs, removable media and transient devices are another form of low hanging fruit, especially if your network is “air gapped” or heavily controlled. Users WILL bypass your controls by way of removable media. As a best practice, system policies are easily deployed, whitelisting software used, registered secure drives, and other technology such as 802.X ensure authorized systems are allowed on network segments.

  • Network Defense
    • Network segmentation and access controls: Limiting network access between zones, conduits, devices, and even business units/function is a critical mechanism for reducing the spread of a ransomware infection. After all, it works in real life preventing/slowing the spread of infectious diseases, adds a barrier to limit initial infection – so it also applies to malware and attackers as well.
    • Monitor network, system and application logs for anomalies: An attack often has precursory elements that indicate an infection. However, it could indicate a vulnerable system that is amidst an attack or is about to be compromised giving your defensive team an advantage to prevent a wide-scale infection or attack.
    • Technical diversity between zones or systems: Consistency across systems has scaling advantages, but when a single vulnerability affects multiple products, this strategy grounds your entire operations if exploited. Barriers such as a VPN with 2FA, a remote access terminal server, and multiple firewall vendors, exponentially increases the efforts if it is an external attack, or from a network zone that has a lot of churn.
  • Access Control
    • Isolated systems based on software, user role, and function: To protect systems compromised through remote access, local Windows networking flaws (e.g., print spool or SMB/NETBIOS), or Office/Acrobat, isolate them based on function and ensure unnecessary software is NOT included in standardized golden images or the same AD server is not serving policy for IT and OT. This also applies for user-based accounts; if an HMI is an HMI, treat it’s operator as an operator, not as an administrator.
    • Monitored external attack surfaces: Many attacks are successfully accomplished due to a misconfiguration or an inadvertent hole caused by a gap in change management. It is a best practice to monitor for exposed services (e.g., Shodan).

  • Backup and Recovery
    • Expanded backup coverage and frequent snapshots (more hosts): The more hosts that are frequently backed up SECURELY, and assuming an adequate pipeline to get systems back those backups (e.g., enough network bandwidth), the faster you can recover from a ransomware attack. However, you must ensure the vulnerability is mitigated or the host is isolated when the backup is restored, or they may become re-infected.
    • Have offline backups of critical assets: Offline backups as a resilience or disaster recovery strategy is critical to ensure your most important crown jewels are protected or can be readily restored if your infrastructure is down. This includes PLC logic code, configuration, documentation, and system images/files. It may sound expensive, but it is often accomplished with securely encrypted USBs that are periodically rotated such that file integrity is maintained.
  • Well-Defined and Tested Policies and Procedures
    • Well-defined and well-tested processes for cyber security in IT & OT: Cyber security processes for traditional IT or even the physical aspects of OT are usually well-defined. However, when it comes to OT, or even handling cyber events and incidents, they are not. Ensure your organization and teams understand the end-to-end processes and identify gaps to ensure escalation or recovery will go without a hitch. When you need them, you need them.
    • Regularly have “cyber fire drills” to test backups and their recovery: Again, I cannot stress this enough, a frequent training regime should be absolutely applied for OT and cyber related events. Forensics, failed hardware, shutdowns etc. should have at least an initial note for cyber, just to ensure it was not cyber-related, and if so, chain of custody and due diligence can be assured. Secondly, it is important that your resources know what to do when there is an issue, so this is another way to double check processes while improving the likelihood of a quick recovery.

Improving these five categories reduces the risk of a ransomware infection, leverages existing technology investments and improves recovery in the event of a compromise. These are all likely to be standard in an OT cyber security program, but also hinge on effective cyber security controls, products, and services should you need them.


Ransomware Data Sheet
OT cyber security expertise, trends and best practices to protect your industrial systems

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