Explanation
A limitation of intrusion detection systems (IDS) is that they cannot detect application-level vulnerabilities. An IDS is a tool that monitors network traffic or system activity and alerts on any suspicious or malicious events.
However, an IDS cannot analyze the logic or functionality of applications and identify vulnerabilities such as SQL injection, cross-site scripting, or broken authentication.

Explanation
In public key cryptography, digital signatures are primarily used to prove sender authenticity. A digital signature is a cryptographic technique that allows the sender of a message to sign it with their private key, which can only be decrypted by their public key. The recipient can verify that the message was sent by the sender and not tampered with by using the sender's public key.

Explanation
Elliptic curve cryptography (ECC) is a more efficient form of public key cryptography as it demands less computational power and offers more security per bit. ECC is based on the mathematical properties of elliptic curves, which are curves that have a special shape that makes them suitable for cryptography. ECC can achieve the same level of security as other public key algorithms with much smaller key sizes, which reduces storage and bandwidth requirements.

Explanation
An information security procedure that indicates a requirement to sandbox emails means that the emails need to be isolated and tested for malicious content. This is because sandboxing is a technique that creates a virtual or isolated environment, where suspicious or untrusted emails can be executed or analyzed without affecting the rest of the system or network. Sandboxing helps to detect and prevent malware, phishing, or spam attacks that may be embedded in emails, and protect the users and the organization from potential harm. The other options are not what sandboxing emails means, but rather different concepts or techniques that are related to information security, such as encryption and nonrepudiation (A), backup and recovery (B), or firewall and delivery (D).

Explanation
A feature of an intrusion detection system (IDS) is automated response. This is because an IDS is a system that monitors network or system activities for malicious or anomalous behavior, and alerts or reports on any detected incidents. An IDS can also perform automated response actions, such as blocking traffic, terminating sessions, or sending notifications, to contain or mitigate the incidents. The other options are not features of an IDS, but rather different concepts or techniques that are related to intrusion detection or prevention, such as intrusion prevention (A), interface with firewalls C, or back doors into applications (D).