Which of the following is a characteristic of SSIDs in wireless networks?

SSIDs, or Service Set Identifiers, are essentially the names given to wireless networks, allowing devices to identify and connect to them. One of the key characteristics of SSIDs is that they are not signed, which means that they lack inherent authenticity. This makes them susceptible to spoofing, where an attacker can create a rogue network with the same SSID as a legitimate one, leading users to unknowingly connect to the malicious network. This presents a significant security risk, as it can facilitate various types of attacks, such as man-in-the-middle attacks.

The other characteristics provided in the options do not accurately describe SSIDs: SSIDs themselves are not encrypted, and while networks can have unique names, the uniqueness is not guaranteed across all devices or networks. Moreover, there is no requirement for SSIDs to be registered with Internet Service Providers (ISPs), as they are typically managed locally by the network administrator or the user setting up the wireless network.