Air Force

Thwarting hardware based cyber attacks

Protecting communications over command/response busses

Software & Information Technology

Computer busses transfer data between components. The MIL-STD-1553 bus uses electrical signaling and the MIL-STD-1773 bus uses optical signaling. Nearly all mission-essential subsystems on military aircraft communicate with one another over one of these two types of busses. Each of these subsystems may come from different manufacturers—some more trustworthy than others—and each of the components that make up each subsystem may also come from individual sources that may or may not be trustworthy. Of concern is that subsystems on shared data busses may see and hear everything that goes on between every other subsystem and the bus. Further, subsystems connect to the MIL-STD-1553 bus through a standard two-conductor connector that may allow them to listen in on communications of unrelated subsystems and may allow them to jam the bus either intentionally or unintentionally. Subsystems may be faulty when installed, develop faults after installation, or may be maliciously engineered to allow for remote access and control through, for example, RF channels.

Air Force scientists and engineers have developed an apparatus and system to use the single, existing, connection to the shared common bus to provide improved and secure bus communications on a shared data bus. The device uses a data transfer filter configured to isolate a remote terminal (RT) from bus controllers and additional RTs residing on a shared host data bus. The data transfer filter enforces a series of rules regulating communications between the RT and the bus controllers and additional RTs.

The in-line filters null or squelch messages determined to be irrelevant or inappropriate. They can apply other mitigating actions that may be taken in response to inappropriate messages. Examples of such include sending error messages over the shared data bus, raising a signal on an independent discrete line, sounding an alarm, disabling an RT, blowing a fuse on a link for a physical disconnection, and combinations of these actions.

While the Air Force will use this technology on aircraft, other systems such as heating, ventilation and air conditioning systems, industrial machinery systems, elevators, and supervisory and data acquisition systems may all benefit from this approach. Other industries and systems that may employ this include commercial aircraft, UAVs, ships, trains, and railway control systems. Many systems are complex and comprise interacting subsystems. In these systems, guaranteeing proper operations in the face of failures and attacks may be challenging. This Air Force invention can provide endpoint protection that can come into play when system-level protections fail and thus limit the threats that the endpoints may present to the overall system.

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