Which protocols are commonly monitored by IDS?

The selection of protocols commonly monitored by Intrusion Detection Systems (IDS) encompasses those that are integral to internet and network communication, making option B the correct answer.

TCP/IP serves as the foundational suite for internet communication, and monitoring it is essential for detecting many types of network-based attacks. HTTP and FTP are both critical protocols for web traffic and file transfers, respectively, which are frequent targets of attacks. DNS is vital for resolving domain names to IP addresses, and monitoring it can help identify potentially malicious activities, such as DNS poisoning or any abnormal queries.

In contrast, while the other options include protocols that an IDS can monitor, they do not offer the same breadth of coverage concerning generalized network traffic that is relevant to the majority of security incidents. For example, individual protocols like IMAP, POP3, and Telnet (found in one of the other options) are more specific to certain types of communications and may not represent the overall landscape of threats as holistically as the selections in option B do.