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

Information Assurance—The Department of Defense Directive 8500.1 ∗ defines information
assurance as “Measures that protect and defend information and information systems by ensuring
their availability, integrity, authentication, confidentiality, and non-repudiation. This includes
providing for restoration of information systems by incorporating protection, detection, and
reaction capabilities.” Several synonyms to IA exist: IT security and information systems
security.
Likelihood—Indication of the probability that a potential vulnerability may be exercised within
the construct of the associated threat environment.
Logical network system—As used in this study, a logical network system is a partitioned
network. Synonymous term is network enclave, e.g., a VPN.
National Information Assurance Partnership—A joint activity of National Institute of Standards
and Technology (NIST) and NSA to establish an IT product security evaluation program based
on the CC. This program is supported by a number of accredited, independent testing
laboratories.
Physical network system—The physical media and intermediate system devices (e.g., router,
bridge, hub) that physically create an actual functioning network. For example, LANs and/or
WAN entities connected into a common network system. Physical network systems are the
network system elements that physically convey network packets.
Risk—“Risk is a function of the likelihood of a given threat-source’s exercising a particular
vulnerability, and the resulting impact of that adverse event on the organization.” (NIST 800-30
Risk Assessment)
Risk assessment—“Risk assessment is the first process in the risk management methodology.
Organizations use risk assessment to determine the extent of the potential threat and the risk
associated with an IT system throughout its lifecycle. The output of this process helps to
identify appropriate controls for reducing or eliminating risk during the risk mitigation process.”
(NIST 800-30 Risk Assessment)
Severity—A measure of the effect of a failure condition on either the airplane or its occupants,
including: (1) reduction in airplane safety margins or airplane functional capabilities including
possible maintenance activity, (2) increase in flight crew workload or conditions impairing flight
crew efficiency, and (3) distress or injury to airplane occupants.
SYN—The synchronous (SYN) bit in the TCP protocol header is used to establish TCP
connections. In session establishment, it is associated with the acknowledgement (ACK) bit. A
TCP connection request has SYN=1 and ACK=0 to indicate that the piggyback
acknowledgement field is not in use. The connection reply does bear an acknowledgement, so it
has SYN=1 and ACK=1. Therefore, the SYN bit is used to denote a connection request and a
∗
Department of Defense Directive (DoDD) 8500.1, “Information Assurance (IA),” October 24, 2002, ASD(C3I),
http://west.dtic.mil/whs/directives/corres/pdf2/d85001p.pdf
159