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Security doesn’t happen by accident – it must be built into or added to a network. Some of the key security building blocks for wired and wireless networks include encryption, authentication, intrusion detection, controlled access to network resources, and wireless airtime and bandwidth control.
Sensor and control networks are typically missing most of these building blocks. Designed to optimize response time, the short packets cannot easily accommodate the larger packet sizes associated with high security encryption.
Some controls networks, LONWORKS® for example, include an authentication mechanism, but in practice it is infrequently implemented because its use complicates key management in multi-vendor networks. Intrusion detection, for wired or wireless control networks, is typically not available, nor is firewalling or endpoint compliance – certainly not at the sensor/actuator level, and sometimes not even at the controller level.
Quick fixes to address these limitations are not easily incorporated because the protocols employed are often embedded inside microprocessors that lack the processing power and memory to support the necessary security algorithms, buffers, and certificates.
Fortunately most control networks today interface with an IP-based network for management, monitoring, and/or control. And it is at this interface that you can click the ruby slippers and apply proven security techniques like policy-enforcement firewalling to prevent the control network from launching Denial-of-Service (DoS) attacks or non-compliant devices from accessing the network.
If the control network is IP-based then the protective measures can be applied to the control devices themselves – if not, then protection can only be applied to data traversing the interface between the sensor/actuator network and the IT systems to which it is connected, i.e., the latter can be protected against the former. Either way, greater security will be obtained than if no protective measures were applied between the control devices and the network with which it is connected.
The range of available security features that may be applied depends on the control network architecture, and includes:
The protective measures afforded by these techniques can be applied prophylactically to reduce some or most of the control system’s vulnerabilities.
With regard to cost, if Wi-Fi based sensors and actuators are used, the protective measures built into the wireless LAN infrastructure can be applied at little or no additional expense. If IP-based sensors and actuators are used, there will be some incremental expense but the devices themselves will not have to replaced because they already have the essential building blocks for higher security in place. If a non-IP based control network is used then the benefits will vary.
The table below summarizes how the security features described above can be employed to enhance the security of commonly used in control networks (features specific to wireless networks are left blank when applied to wired control networks).
Conclusion
SCADA, smart grid, and energy management systems sit at the heart of industry and commerce. This blog series was intended to highlight that defending these systems against attack must become a high priority because you can't use what you can’t control.
The control networks on which these systems depend today have unintended vulnerabilities. These vulnerabilities can be corrected in whole, part, or not at all depending on the architecture and technology of the underlying network.
Consideration should be given to retrofitting security systems into existing IT infrastructure to address security concerns, removing control networks for which there are no corrective measures, and ensuring that any new control-related infrastructure is designed with protective measures built-in from the outset.
For more information on security solutions that you can apply today please visit Aruba's Web site.
In the beginning, there was cabling - lots of cabling. Every sensor, actuator, and display was connected by a separate cable that grew like a hydra from a controller, the brains of a traditional control system. If a solenoid needed to be triggered in response to the activation of a limit switch then the signal traveled from the limit switch, through cabling to the controller, which processed the information and sent a command to the solenoid over yet another cable.
These direct wired systems were subsequently replaced with time or frequency division multiplex systems that allowed one common cable to be shared among multiple devices. Installation was simpler and less expensive, the controller was more complex and, as before, a central point of failure should its program fail to execute properly.
Next up were intelligent, distributed networks in which devices communicated directly with one another on a peer-to-peer basis, without the need for a central controller. Locally intelligent and able to communicate on shared communication medium with any other device on the network, these networks allowed reconfiguration of system functionality via software download over the network. Peer-to-peer communications allowed the direct exchange of information between any or all of the devices without intervention by any central device, eliminating the single point of failure issue.
Regardless of the specific architecture used, in all cases the objective of the control network was to deliver status information as quickly as possible to all devices that needed updates. The protocols we’re highly optimized for short control packets, and nary a bit was “wasted” on ancillary data or status.
The same optimization guidelines applied to the microcontrollers running the devices. To keep costs down and thereby allow the networks to be pervasively deployed down to the lowest cost sensor/actuator, processors were optimized for high throughput and processing short packets.
The popularity of IP connectivity spawned the development of IP-based control networks in which Ethernet or Wi-Fi forms a backbone for linking different sections of a control network. While controllers were the first devices to sit on an IP network, increasing numbers of native IP sensors and actuators are reaching the market.
Many IT departments prohibit the connection of any IP-based, control-related sensor/actuator, controller, gateway to their corporate networks out of concerns about network integrity and security. IT managers are legitimately concerned that the high offered traffic of control networks, some of which run at 100% channel utilization, will overwhelm their Ethernet networks and cause unintentional denial of services. Others are concerned that control networks, the security standards of which are rarely a high priority, could become unprotected back-doors into the corporate network.
What is rarely if ever discussed is how exposed the enterprise is to unauthorized manipulation of the control devices themselves. These systems control the power at the heart of every business and institution, and it is paramount that they be protected against unauthorized manipulation. It is to this point that we’ll return in the next installment of this series.
This multi-part series discusses the security vulnerabilities of the sensor/actuator controls at the heart of SCADA, smart grid and energy management systems, and proposes a means of containing, if not fully addressing, the limitations of these systems.* * * * * * *
In the 1980s the proximity access card was introduced to the building security market. Until that time, gaining access to high security facilities – including many government agencies – required one to physically insert a magnetic stripe or Wiegand card into a reader.
Proximity card readers from Schlage, Sielox, Indala, and others overcame the inconvenience of swiping a card by using radio energy to sweep the area in front of the reader. Users needed only to place their wallet, purse, valise, or ID badge near a reader and the radio energy would be picked up by their proximity card.
A tuned circuit internal to the card would resonate when within range of the reader, generating a unique radio signature that would be captured and analyzed by the access control system. If the signature matched that of a valid card already programmed into the system, access would be granted. Simple, elegant, and convenient, proximity card systems quickly grew in popularity.
Problem was, this innovative technology had profound, unintended consequences. It allowed the surreptitious identification of people with access privileges to high security facilities. One could use radio energy to sweep a crowd of people and, by virtue of their proximity card, pick out persons of interest based on their signatures generated by their proximity cards. At a time when the Cold War was steamy hot and espionage was rampant, the proximity card was a new-found tool for adversaries.
The unintended consequences of a new technology are not usually discovered until after it's in use, sometimes widespread use, by which time available remediation options might be limited or very expensive. Such is the case with SCADA, smart grid, and energy management systems, which are now front and center in the effort to better manage energy consumption and lower greenhouse gases. Unintentionally vulnerable to manipulation and unauthorized access, these systems can literally turn out the lights, stopping a utility or enterprise cold in its tracks.
(Photo: www.brightsecuritygroup.com)
Security doesn’t happen by accident – it must be built into or added to a network. Some of the key security building blocks for wired and wireless networks include encryption, authentication, intrusion detection, controlled access to network resources, and wireless airtime and bandwidth control. 
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