Confidentiality is the principle that is at risk when a digitally-signed e-mail is delivered over a wireless network protected with Wired Equivalent Privacy (WEP) protocol. Confidentiality is the principle that ensures that the data or information is only accessible or disclosed to authorized parties, and that it is protected from unauthorized access or disclosure. WEP is an outdated and insecure protocol that encrypts the wireless network traffic using a shared key that can be easily cracked or compromised by attackers. If an attacker intercepts the wireless network traffic, they can decrypt the WEP-encrypted packets and read the contents of the e-mail, which may contain sensitive or confidential information. The other options are not correct.
Availability is the principle that ensures that the data or information is accessible or available to authorized parties when needed, and that it is protected from denial-of-service or disruption. Availability is not at risk in this scenario, as the e-mail is successfully delivered to the intended recipient. Non-repudiation is the principle that ensures that the origin or authenticity of the data or information can be verified and proven, and that the sender or the receiver cannot deny sending or receiving the data or information. Non-repudiation is not at risk in this scenario, as the e-mail is digitally-signed by the sender, which provides a cryptographic proof of the sender's identity and the integrity of the e-mail. Integrity is the principle that ensures that the data or information is accurate, complete, and consistent, and that it is protected from unauthorized modification or corruption. Integrity is not at risk in this scenario, as the e-mail is digitally-signed by the sender, which provides a cryptographic checksum of the e-mail that can be verified by the receiver to detect any tampering or alteration of the e-mail. References: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 5:
Communication and Network Security, page 566. Official (ISC)2 CISSP CBK Reference, Fifth Edition, Chapter 5: Communication and Network Security, page 567.