Flexible resources are assets that can be adjusted quickly to match changing conditions. In energy systems, that can mean battery storage, controllable load, or demand response. In cyber security, the same idea applies to compute, bandwidth, storage, and worker capacity that can be shifted, scaled, or paused to keep a service stable when demand changes suddenly.
They matter because attackers often try to create imbalance: a flood of traffic, a burst of malicious requests, or a noisy event that exhausts fixed capacity. Defenders use flexible resources to absorb spikes, reroute traffic, isolate systems, and preserve service while incidents are investigated. In cloud and large-network environments, automation may spin up extra capacity or trigger demand response style controls to reduce pressure. The goal is the same in both domains: keep supply and demand aligned fast enough to avoid collapse, outage, or unsafe overload.