Local Area Networks (LANs) in Aircraft - FTP Directory Listing - FAA

Aircraft network security is a systems issue. System development (ARP 4754), in conjunction
with the system safety assessment process (ARP 4761), is responsible for defining network
accesses, vulnerabilities, detection, and protection requirements. Some of the vulnerabilities will
be mitigated by limiting and controlling access by using hardware and software capabilities.
Some identified vulnerabilities will be mitigated by monitoring and detection capabilities. The
security protection should be defined by the system and then by appropriate system requirements
allocated to hardware, software, and hybrids. This study assumes that best current IA practice
will be followed, including deployment of traditional IA security controls when appropriate.
After implementation, these protections, mitigations, and monitoring will also likely be verified
and validated at the system level, as well. Consequently, aircraft network security is an ARP
4754 issue.
However, approving networked systems in some ways should be recognized as being a
significant extension to ARP 4754. Networked systems differ from the current ARP 4754
environment in several significant ways. Networked elements are systems that include all of the
networks and their constituent elements and users to which the network is directly or indirectly
attached. Networks are therefore arbitrarily huge, and the many interrelationships of the system
items are often too subtle to discern. Networks are inherently complex systems in which every
item in the network is inadvertently integrated, regardless of whether those items share any
common functional goal. Approval of networked entities must now also address possible
network interactions that occur during, and result from, network attacks. The various networked
elements potentially have a fate sharing relationship with each other, because any compromised
network entity theoretically can be used to attack other networked items or their shared network
environment.
Therefore, networked airborne LAN environments are inherently “highly integrated or complex
aircraft systems,” with attributes that extend the complex relationships for which ARP 4754 was
created. Section 4 and appendix A will introduce some of the risks that characterize networked
systems and underlie the following observations:
• In networked environments, ARP 4754 needs to be extended to consider each item within
the LAN to be integrated, even if that item has no functional relationship with anything
else. For example,
- If the LAN experiences a successful denial of service (DoS) attack, then each
networked item in that LAN may potentially be unable to fulfill its function.
Therefore, ARP 4754 must be extended in networked environments to ensure
availability.
- If an item in the LAN becomes hostilely compromised by an attacker, then it
potentially can be used by that attacker to attack the network itself or other items
on the LAN. Therefore, ARP 4754 must be extended in networked environments
to address LAN and item integrity. To ensure LAN and item integrity, ARP 4754
needs to be extended to require verifiably secure software installation procedures
as well as mechanisms to ensure the continued integrity of deployed items and
systems.
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