Krack is a security vulnerability that affects the Wi-Fi Protected Access II (WPA2) protocol, which is widely used to secure wireless networks. Discovered in 2017, this flaw allows attackers to intercept and manipulate data transmitted over a Wi-Fi connection, potentially compromising sensitive information such as passwords and personal data. The name "Krack" stands for "Key Reinstallation Attack," as it exploits the way devices handle cryptographic keys during the connection process. By forcing a device to reinstall an already-in-use key, an attacker can decrypt and inject data into the communication stream, making it crucial for users to update their Wi-Fi devices and routers to mitigate this risk.