Interstellar space is the region between stars. It contains extremely little matter, so signals, particles, and radiation are sparse compared with planetary environments. In astronomy, that low density makes detection difficult and forces analysts to rely on careful measurement and context.
In cybersecurity, the term is often used as a useful analogy for sparse telemetry: a single log line, unusual packet, or rare authentication event may be meaningful, but only if it is interpreted conservatively. Attackers can hide in low-noise environments by moving slowly, using few connections, or blending into expected gaps. Defenders respond by correlating weak signals across sources instead of overreading one clue. The lesson is simple: when data is rare, discipline matters more than certainty.