To determine whether data exfiltration has occurred, the most effective tool is a packet capture (PCAP). Packet captures allow investigators to see exactly what data left the network, including file contents, payloads, headers, protocols, and destination information. PCAP files provide full-fidelity network evidence, enabling analysts to reconstruct sessions and review exfiltrated content byte-by-byte.

Security+ SY0-701 emphasizes PCAP as the gold standard for forensic network investigations, especially when dealing with:

Malware beaconing

Command-and-control (C2) traffic

Data leakage

Unauthorized transmissions

Network logs (C) provide summaries such as IP addresses, ports, and timestamps but do not show actual data contents. Metadata (B) gives descriptive information (e.g., file size, type) but not transmitted payloads. Application logs (A) show application-level events but do not capture network data.

If the analyst needs to confidently determine if sensitive information was exported to the attacker, only packet capture provides the required depth of visibility.