What is the effect of setting a wireless router's security mode to WEP?

Setting a wireless router's security mode to WEP (Wired Equivalent Privacy) primarily serves the purpose of encrypting data as it travels between the wireless client and the access point. This encryption is intended to safeguard the information being transmitted over the airwaves from eavesdropping, making it more difficult for unauthorized users to intercept or read the data packets.

While WEP does provide a level of encryption, it's worth noting that its security has significant weaknesses and is largely considered outdated compared to more modern protocols such as WPA (Wi-Fi Protected Access) and WPA2. However, in the context of the question, the key point is that enabling WEP does indeed allow for data encryption, which protects the integrity and confidentiality of the communication between devices on the wireless network.

The other options do not accurately reflect the primary function of WEP. For example, WEP does not inherently provide network visibility, block external connections, or boost signal strength; those functions relate to different aspects of network management and security protocols.