The presence of a default user agent in the headers of requests and data being transmitted suggests a cache bypassing attack. In this scenario, the attacker is likely requesting noncacheable content to avoid detection by caching mechanisms that could otherwise identify and block malicious traffic.

Phishing is considered a low-bandwidth attack because it does not require the use of significant network resources. Instead, it relies on social engineering to deceive individuals into providing sensitive information or clicking on malicious links, often through email or other communication methods1.

When an analyst needs to quickly assess a historical security event on a busy network segment, efficiency and scalability are critical. NetFlow is specifically designed to support rapid, high-level analysis of network activity without requiring deep packet inspection.
NetFlow provides summarized metadata such as source and destination IP addresses, ports, protocols, timestamps, and volume of data transferred. This information allows engineers to quickly identify suspicious hosts, unusual traffic patterns, and the scope of potential incidents-even when they have little prior context.
Because NetFlow data is compact, indexed, and optimized for querying, it is far more suitable for fast analysis over long time ranges, such as a full month.
In contrast, .pcap files contain full packet payloads and generate massive data volumes, especially on busy network segments. Analyzing .pcap data without a specific hypothesis is time-consuming and computationally expensive, making it impractical for quick triage or broad scoping.
Cybersecurity operations documentation emphasizes NetFlow as the preferred data source for initial investigation, scoping, and rapid situational awareness, with packet captures reserved for deeper forensic analysis once suspicious activity has been identified.
Therefore, NetFlow is the correct choice for fast, efficient analysis in this scenario.