What Is Network Traffic Analysis?
Network traffic analysis is the process of capturing, inspecting, and interpreting network traffic to understand how data flows across a system. It helps security teams find potential threats and network engineers solve performance issues like packet loss or high latency.
The goal is simple: learn useful information about how traffic moves across a network. These insights can find security problems and operational problems before they get worse.
How traffic moves around can be different depending on how the network is set up, how people use it, and outside factors. For example, changes in the way data is sent between different parts of a network can cause sudden increases in network latency. On the other hand, if someone tries to attack the network (for example, by scanning ports or launching a denial-of-service attack), that person will often leave behind a unique set of traffic patterns. It’s very important to spot these problems early on so that we can defend ourselves and keep things running smoothly.
How Network Traffic Analysis Works
Network traffic analysis typically includes the following steps:
- Establish a baseline: First, network operations teams monitor the network during periods of normal activity to understand what typical network traffic patterns look like.
- Anomaly identification: Ongoing monitoring makes it possible to detect anomalies, such as unusual types of traffic flows or requests.
- Anomaly analysis: Not all anomalies within network traffic signify a problem. Therefore, when an anomaly is detected, engineers must investigate it to determine whether it results from a benign cause (such as the deployment of a new application that results in traffic pattern changes) or a problem. Problems could constitute performance issues (such as a failed router or switch that causes packets to be routed in unexpected ways) or security issues (like a network scan by malicious actors).
To work well at scale, network traffic analysis processes should be automated. This can be done by pairing automated monitoring tools with rule-based detection engines that can detect deviations from normal traffic patterns.
A Hands-On Case Study: Analyzing Suspicious Traffic
To better understand how network traffic analysis works in practice, let’s walk through a basic case study using Wireshark, one of the most widely used tools for inspecting packet captures (PCAP files).
The image shows a Wireshark capture window displaying network packets from the file traffic-analysis-example.pcap. The highlighted packet is a DHCP Discover message, the first step in the DHCP process where a device without an IP address (0.0.0.0) broadcasts a request to find a DHCP server (255.255.255.255). This kind of traffic is expected during device boot or network reattachment, and it’s essential when building a baseline of normal network behavior. The message is sent via UDP from port 68 to port 67, using the MAC address of the client (ASUSTeKCOMPU_32:58:f9). Analyzing such packets allows network engineers to verify proper address assignment, detect misconfigurations, or identify unauthorized devices joining the network. Wireshark displays both the decoded protocol layers and the raw hex data, showcasing how even basic traffic like DHCP can provide valuable visibility into device activity and network operations.
In the screenshot above, we see a series of HTTP POST requests sent from a local machine (192.168.1.216) to a remote IP address (2.56.57.108). Each request targets a different .jpg file under the /osk/ directory, such as /osk/1.jpg, /osk/2.jpg, and so on. While the file extensions suggest image uploads, the repeated pattern, short time intervals, and use of the multipart/form-data content type indicate potentially suspicious behavior. This traffic could be part of a scripted or automated process, possibly related to data exfiltration where sensitive information is disguised as image files. The absence of a domain name and the use of plain HTTP (without encryption) further raise concerns about the legitimacy of the destination. With Wireshark, such patterns become easy to detect through simple filters like http.request, making it a powerful tool for identifying anomalies that may signal security threats such as malware communication or command-and-control activity.
One of the most powerful features of traffic analysis with Wireshark is the ability to inspect the actual application-layer payload, especially when unencrypted protocols like HTTP are involved. In the screenshot above, by applying a simple filter (frame contains "password"), we can pinpoint TCP packets containing potentially sensitive data exchanged between a remote server and a local host. The reassembled payload reveals textual strings including variables, SQL commands such as DROP TABLE IF EXISTS, and explicit references to security-related metadata like password, private, and sig. Unfortunately, this kind of exposure is still common in many legacy or misconfigured applications, highlighting the risks of transmitting data in plaintext over unsecured networks. Wireshark, therefore, is not just a diagnostic tool but a crucial ally in safeguarding security and privacy, a single well-crafted filter can unveil critical vulnerabilities that might otherwise go unnoticed.
Conclusion
Network traffic analysis lets us see how digital systems work. By watching how data moves across the network, we learn important things. These things help us improve performance and find threats. As we can see, even common protocols like DHCP or HTTP can show problems or signs of malicious activity if we look closely at them. Wireshark is a tool that helps analysts turn raw traffic into useful information. This helps them respond faster and make better decisions. As networks become more complex, it becomes very important to have this level of visibility.
