What is a replay attack?

A replay attack is defined as an attack where an unauthorized party intercepts a data transmission and then retransmits it at a later time, effectively "replaying" the communication. This type of attack exploits the fact that certain network protocols may not sufficiently authenticate the origin or the time frame of the data packets being sent.

In practical terms, a replay attack may involve capturing a valid data transmission, such as a password or a transaction request, and then sending that exact data to the recipient or server again. This can lead to unauthorized actions being executed, as the system may treat the re-transmitted data as legitimate and valid, thereby compromising security.

This understanding of a replay attack is crucial for implementing robust security measures, such as using time-stamps or unique session tokens that ensure that messages cannot be reused without detection. Other options, while related to different types of attacks or security breaches, do not accurately define the concept of a replay attack within the context of data transmission and network security.