wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

22-2 Industrial Communication Systems
a security threat. While a security attack is the actual action that tries to violate the security of a system,
a security threat is the potential for violation of security that may never be utilized [R49].
Up to now, security has been neglected in the industrial communication domain. However, as mentioned
in [DZU], industrial communication systems are already the target of security attacks as reported
incidents show. The consequences of a successful security attack on an industrial communication system
may be manifold. In addition to a malfunction of safety critical services, which are harmful to
humans, security attacks on industrial communication systems can also have massive economic impact.
Consider, for example, a power plant being the target of a security attack.
Since security has been a major topic in the Information Technology (IT) world for years, many available
security mechanisms exist. However, it is not always possible to trivially map these mechanisms
to the industrial communication domain. This is for various reasons. The requirements regarding the
used communication protocol(s) may differ. Industrial communication systems often have real-time
and safety requirements that cannot be met by protocols and their extensions used in the IT world.
Additionally, while Internet protocol (IP)-based networks are getting more popular in industrial communication
systems, non-IP-based fieldbus media and protocols are still used at the field level. Since
most IT security mechanisms are tailored to IP networks, they are of limited use in non-IP-based fieldbusses.
Furthermore, in contrast to devices typically found in the IT domain, industrial communication
systems may consist of low-power embedded devices with limited system resources. This is especially
true in wireless sensor networks. Since security mechanisms are computationally intensive, their use
must not exceed the available resources of these embedded devices.
Industrial communication systems are distributed systems where the control functionality is spread
across different devices. To interact with each other, these devices are interconnected by a common
network. Therefore, an adversary has two different opportunities to gain unauthorized access to control
functions: The adversary may try to maliciously interfere with the data that is exchanged between the
devices (network attacks) or the adversary may directly attack the devices that implement the control
functionality (device attacks).
Network attacks can be divided into four classes [PFL]:
• Interception attacks: The adversary tries to gain unauthorized access to confidential data
exchanged over the network (e.g., network sniffing).
• Modification attacks: The adversary tries to change the data while it is transmitted over the network
(e.g., modification of network messages).
• Fabrication attacks: The adversary tries to insert malicious data (e.g., replay previously sent network
messages).
• Interruption attacks: The adversary tries to interrupt the communication between devices and
thus makes data unavailable (e.g., denial-of-service (DoS) attacks).
Device attacks, on the other hand, can be classified into
• Software attacks: An adversary may use regular communication channels to exploit weaknesses
in a device’s software.
• Physical attacks: An adversary may use physical intrusion or manipulation (e.g., probing of bus
lines, replacement of ROM chips) to interfere with a device.
• Side-channel attacks: Side-channel attacks are based on observing external parameters of a device
such as current consumption of EM emissions that are measurable during operation to collect
information about its internals.
To counteract these types of security attacks, different security objectives have to be guaranteed.
According to [DZU], these are integrity, availability, authentication, authorization, confidentiality, and
non-repudiation or traceability, whereas the first four have a very high ranking in industrial communication
systems.
© 2011 by Taylor and Francis Group, LLC