Environmental Engineering Reference
In-Depth Information
of network security. Organization management must understand
and accept responsibility or risks associated with any connection to
the SCADA network.
4. Harden SCADA networks by removing or disabling unnecessary services.
SCADA control servers built on commercial or open-source oper-
ating systems can be exposed to attack through default network
services. To the greatest degree possible, remove or disable unused
services and network demons to reduce the risk of direct attack.
This is particularly important when SCADA networks are intercon-
nected with other networks. Do not permit a service or feature on
a SCADA network unless a thorough risk assessment of the conse-
quences of allowing the service or feature shows that the benefits
of the service or feature far outweigh the potential for vulnerabil-
ity exploitation. Examples of services to remove from SCADA net-
works include automated meter reading/remote billing systems,
e-mail services, and Internet access. An example of a feature to dis-
able is remote maintenance. Refer to the National Security Agency's
series of security guides. Additionally, work closely with SCADA
vendors to identify secure configurations and coordinate any and
all changes to operational systems to ensure that removing or dis-
abling services does not cause downtime, interruption of service, or
loss of support.
5. Do not rely on proprietary protocols to protect your system. Some SCADA
systems are unique, proprietary protocols for communications
between field devices and servers. Often the security of SCADA sys-
tems is based solely on the secrecy of these protocols. Unfortunately,
obscure protocols provide very little real security. Do not rely on
proprietary protocols or factor default configuration settings to pro-
tect your system. Additionally, demand that vendors disclose any
backdoors or vendor interfaces to your SCADA systems, and expect
them to provide systems that are capable of being secured.
6. Implement the security features provided by device and system vendors .
Older SCADA systems (most systems in use) have no security fea-
tures whatsoever. SCADA system owners must insist that their
system vendors implement security features in the form of product
patches or upgrades. Some newer SCADA devices are shipped with
basic security features, but these are usually disabled to ensure ease
of installation. Analyze each SCADA device to determine whether
security features are present. Additionally, factory default security
settings (such as in computer network firewalls) are often set to pro-
vide maximum usability but minimal security. Set all security fea-
tures to provide the maximum security only after a thorough risk
assessment of the consequences of reducing the security level.
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