Replay attack
In web security, a replay attack happens when an attacker intercepts a previously-sent message and resends it later to get the same credentials as the original message, potentially with a different payload or instruction.
Replay attacks can be prevented by including a unique, single-use identifier with each message that the receiver can use to verify the authenticity of the transmission. This identifier can take the form of a session token or "number used only once" (nonce).
Prevention Example
A typical prevention strategy includes a timestamp and nonce in requests:
http
Authorization: Bearer token123
X-Request-Timestamp: 1703001234
X-Request-Nonce: abc123xyz
The server rejects requests with expired timestamps or previously-used nonces.
See also
- Replay attack on Wikipedia.