An FPGA, or field-programmable gate array, is a reconfigurable chip that can be programmed to behave like custom hardware. Instead of running software instructions like a CPU, it implements logic directly in silicon through a configuration file called a bitstream. That makes FPGAs useful when timing, parallelism, or exact device behavior matters.
In cyber security, FPGAs matter because they can be used both defensively and offensively. Defenders deploy them in network appliances, packet filters, and high-speed inspection tools where low latency is important. Attackers may abuse them for stealthy processing, hardware implants, or to mimic trusted devices. Security teams therefore care about bitstream provenance, firmware integrity, and access to debug interfaces such as JTAG. A tampered configuration can change what the hardware really does, so FPGA builds should be treated as sensitive supply-chain artifacts, not just ordinary files.