IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Hardware & Software Remarks
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S 4.82 Secure configuration of active network
components
Initiation responsibility: Head of IT Section, IT Security Management
Implementation responsibility: Administrators
In addition to the security of server systems and terminal devices, that of the
actual network infrastructure together with its active network components is
often neglected. Particularly central, active network components need to be
configured in a careful fashion. Whereas a faulty configuration of a server
system only affects persons making use of the services offered by this system,
a faulty configuration of a router can lead to a failure of large subnetworks, if
not the entire network, and cause data to be corrupted unnoticed.
A secure configuration of active network components must also be defined as
part of the network concept (refer to S 2.141 Development of a network
concept). Particular attention must be paid to the following items here:
- For routers and layer-3 switching, a decision is required as to which
protocols should be forwarded and which should be barred. This can be
achieved through the use of suitable filters.
- A specification is required as to which IT systems are to communicate in
which direction via the routers. This can also be achieved through the
implementation of filter rules.
- Insofar as it is supported by the active network components, a specification
is also required as to which IT systems are to have access to the ports of the
switches and hubs of the local network. For this, the MAC address of the
calling IT system is evaluated to determine whether the system has been
granted access authorisation.
For active network components with a routing functionality, appropriate
protection of the routing updates is also necessary. These are required for
updating the routing tables in order to allow dynamic adaptation to the current
status of the local network. A distinction can be made here between two
security mechanisms:
- Passwords
The use of passwords prevents configured routers from accepting routing
updates from routers which are not in possession of the corresponding
password. This protects routers against an acceptance of incorrect or
invalid routing updates. The advantage of passwords in comparison with
other protective mechanisms is their low overhead, which only needs a
narrow bandwidth and short computing times.
- Cryptographic checksums
Checksums provide protection against concealed modifications to valid
routing updates as they pass through the network. Together with a
sequence number or a unique identifier, a checksum can also provide
protection against the reloading of old updates.
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IT-Baseline Protection Manual: Oktober 2000