Final answer:
Shared key authentication in a WLAN is a security risk because the pre-shared key is known to all devices, making unauthorized access possible. It also lacks granular control and makes network management and security challenging.
Step-by-step explanation:
Shared key authentication is considered a security risk in a wireless local area network (WLAN) because it relies on a pre-shared key (PSK) that is known to all the devices in the network. This means that if the PSK is compromised, an attacker can gain unauthorized access to the network.
Furthermore, because the same key is used by all devices, there is no way to revoke access for a specific device without changing the key for all devices. This lack of granular control makes it difficult to manage and secure the network.
As an alternative to shared key authentication, it is recommended to use more secure methods such as Wi-Fi Protected Access (WPA) or WPA2 with stronger security protocols like WPA2-Enterprise, which uses individual user credentials for authentication.