Question: What happens to a message when an unsuccessful integrity check is detected in a mobile network?
Option 1: The message is sent back to the sender for retransmission.
Option 2: The message is stored in a buffer for later processing.
Option 3: The message is forwarded to the next hop with a warning flag.
Option 4: The message is discarded and not processed further.
Explanation: In mobile networks, integrity checks are performed to ensure the authenticity and integrity of messages. If an unsuccessful integrity check is detected, it means that the message has been tampered with or corrupted during transmission. To prevent any potential security threats, the concerned message shall be discarded and not processed further, as specified in the 3GPP security architecture.