computers & controls
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These include: network design; regulating physical v Intrusion detection: One problem with Firewalls and
access; firewalls; intrusion detection; virtual private other simple boundary devices currently available is
networks (VPN); IP security (IPSpec) demilitarised their lack some degree of intelligence when it comes to
zones (DMZs). observing, recognising and identifying attack signatures
v Network Design: It is a fact that simple networks that may be present in the traffic they monitor and the
are at less risk than more complex, interconnected log files which they collect. This deficiency explains
networks. Therefore keep the network simple and, why intrusion detection systems, (IDS) are increasingly
more importantly, well documented from the beginning. important in helping to maintain network security.
A key factor in ensuring a secure network is the In a nutshell, an IDS is a specialised tool that
number of contact points. These should be limited as knows how to read and interpret the contents of log
far as possible. While firewalls have secured access files from routers, firewalls, servers and other network
from the Internet, many existing control systems devices. Furthermore, an IDS often stores a database of
have modems installed to allow remote users access known attack signatures and can compare patterns of
to the system for debugging. These modems are often activity, traffic or behaviour it identifies in the logs it’s
connected directly to controllers in the substations. monitoring against those signatures, so it can recognise
The access point, if required, should be through a single when a close match between a signature and current or
point that is password protected and where user action recent behavior occurs.
logging can be achieved. In practice, most commercial environments
v Regulating physical access to the Scada network: use some combination of network- and host- and/
The benefits of a simply designed network can easily or application-based IDS systems to observe what’s
be dissipated if some basic protection strategies are not happening on the network while also monitoring key
followed. For example: physical access to your network hosts and applications more closely.
should be closely monitored. First, do not allow anyone v Virtual private network (VPN): One of the main
that does not belong to your organisation to connect to security issues facing more complex networks today
your network Ethernet or have physical access to your is remote access. VPN is a secured way of connecting
IT server room. Second, use built-in Microsoft Windows to remote SCADA networks. With a Virtual Private
features such as NTFS to require user authentication Network (VPN), all data paths are secret to a certain
when perusing network shares. Third, monitor your extent, yet open to a limited group of persons, such as
network regularly for activity that may be suspicious employees of a supplier company. A VPN is a network
and note the IP addresses when running sniffing constructed by using public wires to connect nodes.
software or hardware on the network. Fourth, ensure For example, there are a number of systems that
that there are no foreign IP addresses on the list. If allow the creation of networks using the Internet as
you find one, trace route to the IP address. Once you the medium for transporting data. These systems use
locate its origin you can take action. If you are unsure encryption and other security measures to ensure only
physically, then disconnect the segment where the authorised users access the network and data cannot be
potential intruder may be on the network. intercepted.
v Firewalls: A firewall is a set of related programs, v IP Security (IPsec): Deployed widely to implement
located at a network gateway server that protects the VPNs is IP Security (IPsec), a set of protocols
resources of a private network from outside users. developed by the Internet Engineering Task Force
A firewall, working closely with a router program, (IETF) to support the secure exchange of packets at
examines each network packet to determine whether the IP layer. IPsec can be deployed within a network
to forward it toward its destination. It also includes or to provide computer-level authentication, as well as
works with a proxy server that makes network requests data encryption. It an also be used to create a VPN
on behalf of workstation users. A firewall is often connection between the two remote networks using
installed in a specially designated computer separate the highly secured Layer Two Tunnelling Protocol with
from the rest of the network, so that no incoming Internet Protocol security (L2TP/IPSec).
request can get directly at private network resources. v Demilitarised zones (DMZ): The use of DMZ buffers
It is imperative to utilise a secured firewall between is becoming increasingly common as a method of
a corporate network and the Internet. As the single segregating business applications from Scada networks.
point of traffic into and out of a corporate network, a A highly recommended additional security measure
firewall can be effectively monitored and secured. It demilitarised zones are a buffer between a trusted
is important to have at least one firewall and router network (Scada network) and the corporate network
separating the network from external networks not in or internet, separated through additional firewalls and
the company’s dominion. routers, which provide an extra layer of security against
On larger sites the control system needs to be cyber attacks. v
protected from attack within the Scada network.
Implementing an additional firewall between the Paul Hurst is with Citect UK, Coleshill, West Midlands,
corporate and Scada network can achieve this aim. UK. www.citect.com
www.engineerlive.com
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