An engineer is investigating a case of the unauthorized usage of the “Tcpdump” tool. The analysis revealed that a malicious insider attempted to sniff traffic on a specific interface. What type of information did the malicious insider attempt to obtain?

tcpdump is a powerful command-line packet analyzer used to capture and display network traffic. When a malicious actor uses this tool for traffic sniffing, their objective is to intercept the raw packets, or datagrams, traversing a network interface. Each datagram contains the complete packet information, including Layer 2 (MAC), Layer 3 (IP), and Layer 4 (TCP/UDP) headers, as well as the application data payload. By capturing the entire datagram, the insider can analyze all protocol information and, if the data is unencrypted, view the actual content being transmitted, such as credentials, messages, or other sensitive information.

A. This is incorrect because protocol information is only one part of a datagram. The tool captures the entire packet, including the data payload, not just protocol tags.
B. tcpdump captures raw network packets. It does not directly capture system-level alerts or mitigation logs from a firewall, which are typically sent to a SIEM or syslog server.
C. This is an incomplete answer. Port numbers are part of the transport layer header within a datagram, but tcpdump captures all headers and the data payload.

1. Official Vendor Documentation (Cisco): In the Cisco Firepower Threat Defense Command Reference

the description of the capture command (which is a tcpdump-like utility) states it "captures packets that are entering or leaving an interface." This confirms the tool's function is to capture the entire packet (datagram).

Source: Cisco

Firepower Threat Defense Command Reference

"capture" command section.

2. University Courseware: Stanford University's CS 144 course on computer networking explains that a packet (datagram) consists of a header and a payload. Packet sniffing tools like tcpdump are designed to capture this entire structure for analysis.

Source: Stanford University

CS 144: Introduction to Computer Networking

Fall 2019

Lecture 5: "Link Layer

" Slide 10 ("A packet has a header and a payload").

3. Peer-Reviewed Academic Publication: A study on network traffic monitoring describes tcpdump as a tool that "captures the complete contents of packets from a network interface." This highlights its ability to access all information within the datagram

not just specific parts like protocols or ports.

Source: Paxson

V. (1999). Bro: A System for Detecting Network Intruders in Real-Time. Computer Networks

31(23-24)

2435-2463. (While discussing its own tool

"Bro

" the paper describes the fundamental function of underlying packet capture mechanisms like libpcap

which tcpdump uses). DOI: https://doi.org/10.1016/S1389-1286(99)00112-700112-7)

Section 2.1.