That the bad guys are capable of storing unlimited amounts of encrypted data on their hard-drives to use it later on. They might try to resend(replay) part of their collection for illegitimate reason (or just for fun). This is also a valid threat. Such attacks are known as "Replay Attacks". Also known as a "man-in-the-middle attack".
If Replay protection will not be supported then what will impact ?
For example, messages from an authorized user who is logging into a network may be captured by an attacker and resent (replayed) the next day. This can trick the receiver into unauthorized operations such as false identification or authentication or a duplicate transaction.
The way to address such an attacks is to have a sequence number in each packet — and have the sequence number included in the packet’s Integrity Check Value (ICV). *Session Token* or *One time passwords* are options to protect user's session data.
