Negative resistance is a circuit behavior where the current-voltage curve appears to slope the “wrong” way: increasing voltage can produce less current over a specific operating range. It is usually not a literal passive resistor with negative ohms, but a property of a device, bias point, or larger network. Engineers encounter it in tunnel diodes, transistor circuits, and feedback systems, where the local behavior can differ from the simple rule taught for ordinary resistors.
In cyber security, negative resistance matters because unstable or oscillating circuits can be exploited or defended against. Attackers may use knowledge of this behavior to push radios, sensors, power regulators, or analog interfaces into unwanted oscillation, noise, or reset conditions. Defenders study it to stabilize hardware, prevent unintended amplification, and spot suspicious components or tampered boards. Understanding the curve helps separate a genuine device characteristic from a measurement artifact and reduces mistakes in hardware analysis, testing, and secure system design.