Electricity + Control September 2017

CONTROL SYSTEMS + AUTOMATION

Using third party infrastructure can be accom- plished in a dedicated manner, meaning that se- cure tunnels through the ISP’s network are dedi- cated to a single customer. Once again, the cost for this sort of service can be restrictive. The third option is to use an existing network that covers the geographic location in question, which in most cases means using the Internet. All options to be properly secure Whilst using a dedicated company network is the most secure method and using the Internet is the least secure, all of these options must be properly secured to ensure that data and devices are properly protected from a variety of attacks, whether direct- ly targeted or random, and whether they are mali- ciously intended or simply the result of human or machine error. For the purposes of talking about se- curity on mission critical networks, an attack should be considered anything that could adversely affect the data on the network, the legitimate users of the network, and any device connected to the network. Network security: Physical level The first level to look at when considering network security is the physical level, which should already be in place as it applies to any type of security. We are of course talking about things like access security and physical disaster recovery. Making sure that unwanted users cannot access physical network devices is obviously a priority, and can be easily accomplished using standard security measures such as walls, fencing, locked buildings etc. Physical disaster recovery is quite straightfor- ward, and includes things like automated or man- ual firefighting systems, back-up UPSs and simi- lar. While this is definitely a highly critical part of network security, it is too obvious and general to warrant more than a quick mention. Logical security Next we need to look at the logical security of the network, which can be roughly broken down into local security (attackers who can get direct phys- ical access to the network and logically access devices that way) and remote security (attackers who are physically connected outside of the local network, and are instead trying to logically breach the network). While these are greatly intertwined and related, it is logical to approach security from a bottom-up approach in most cases.This means we will address local security first. One of the most prolific breakdowns in local security comes from the tendency of users to not change the default authentication details of net-

working devices and attached devices. This means anyone can find the login details with a model number, Google and about five minutes of search- ing. While it is convenient to not have to record and remember a number of passwords, it is im- portant to remember that a certain level of conven- ience has to be forsaken in order to have a properly secure network. Virtual Local Area Networks (VLANs) This leads us to VLANs and their use on networks, as VLANs are probably among the greatest caus- es of confusion in any industrial or utility grade network, and as such are often only partially im- plemented leading to messy and inefficient net- works. A rough breakdown of the need for and operation of VLANs is required. Broadcast One of the fundamental communication types in TCP/IP networks is a broadcast, where a device sends a packet to every other device within its subnet. The problem is that switches, as layer 2 devices, will flood this packet out of every port be- sides the one on which it is received. This means that even devices that are not in the originating device’s subnet will still receive this broadcast packet, even though they are not interested in it. These devices will simply discard the packet, however they first must receive, error check and inspect the packet, which takes up resources. The amount of resources consumed will be tiny, but in very large networks these small bits of wasted

resources add up, and can serious- ly affect critical network traffic. For this reason a method of segregating devices into separate broadcast do- mains is needed. Routers Routers will separate broadcast do- mains, but are not feasible for this ap- plication for a myriad of reasons that are irrelevant to this discussion. In- stead we require an option to segre-

Will the cost and time saved by not implementing a

certain level of security outweigh the potential loss if the security is breached?

gate traffic based on a logical configuration of the switches, which can be adjusted as required and is not hardware based. The solution is VLANs. As the name implies, VLANs logically (virtually) separate the network into different LANs, even though at a physical level these VLANs are still connected. This means that broadcasts will not be sent to de- vices in a separate VLAN at all, as the switch will be configured to not send them, meaning the end devices do not have to assign any resources to in- specting unwanted traffic.

Electricity + Control

SEPTEMBER 2017

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