Wireshark / TShark

Wireshark is the interactive GUI for packet inspection, stream following, and protocol dissection. TShark is the command-line interface built on the same dissector engine, which makes it ideal for automation, SSH sessions, servers, and quick summaries in incident response workflows.

For defenders, these tools answer questions that logs and alerts often cannot: Did a TCP handshake complete? Was DNS resolution successful? Was the TLS handshake negotiated properly? Did the client retry? Which headers were sent? Was the request malformed?

They are especially valuable when multiple systems disagree. A firewall may show accepted traffic, an application may show a timeout, and an IDS may show nothing. A packet capture can clarify whether the issue is routing, retransmission, protocol mismatch, encryption negotiation, or application behavior.

Start with the question you are trying to answer. If the question is service outage, focus on path reachability, retransmissions, resets, and application response codes. If the question is suspicious activity, focus on unusual destinations, protocol usage, session timing, and repeated patterns.

Use a two-stage workflow: first-pass scoping, then deep analysis. In first-pass scoping, identify top talkers, protocols, time windows, and obvious errors. In deep analysis, reconstruct streams, inspect DNS behavior, examine TLS metadata, and annotate exact evidence supporting your conclusions.

Document the capture context every time: interface, capture location, filter used, time window, and what was not visible. This prevents later confusion and makes your analysis repeatable by another analyst.

Wireshark is one of the best places to learn how DNS actually behaves in your environment. You can inspect query names, response codes, resolver choices, retry patterns, and latency. This helps distinguish malicious-looking domains from simple misconfigurations or stale DNS settings.

TLS analysis is equally important even when payloads are encrypted. Defenders can inspect versions, cipher negotiation, certificate metadata, timing, SNI in many environments, and handshake failures. These clues often explain service issues or support network-based detections without decrypting content.

Learn what is and is not visible under encryption. This mindset improves both troubleshooting and threat detection because you stop assuming encrypted traffic is opaque and instead focus on metadata, sequence, timing, and protocol behavior.

TShark is ideal for extracting high-value fields quickly from large captures: DNS query names, TLS SNI, IP conversations, HTTP methods, and protocol counts. This reduces the time spent clicking through traffic when the first goal is to narrow the dataset.

In incident response, you can use TShark to build short evidence tables for reports. For example, a list of suspicious destinations contacted by one host, a count of failed TLS negotiations, or DNS NXDOMAIN spikes over a time window. This helps communicate findings to responders who are not packet analysts.

TShark also supports scripted workflows. Security teams often keep shell snippets or scripts to summarize captures consistently across cases. When you later move to a larger environment, these habits make it easier to scale packet triage without losing rigor.

Capture scope matters more than tool preference. A perfect analysis tool is useless if the capture point misses the relevant traffic. Know whether you are capturing on an endpoint, SPAN port, firewall, VPN concentrator, cloud mirror, or tap, and what blind spots that creates.

Be deliberate with capture and display filters. Capture filters reduce volume at collection time but permanently exclude traffic. Display filters are safer when you are unsure because they preserve data while allowing selective analysis. In high-volume networks, combine short capture windows with targeted filters and documented rationale.

PCAPs may contain regulated or highly sensitive data. Build habits around secure storage, limited retention, and access control. If you use packet captures for training, use lab captures or redacted examples where possible.

Packet tools complement SIEMs, IDS/IPS, and endpoint telemetry. Alerts can tell you something suspicious occurred, but packet evidence helps validate the event, reconstruct sequence, and improve detection logic. This is particularly useful when tuning IDS signatures or writing protocol-aware detections.

In mature workflows, Wireshark and TShark support three recurring tasks: service troubleshooting, alert validation, and forensic reconstruction. Teams that treat packet analysis as a normal skill rather than a rare escalation capability resolve incidents faster and produce higher-quality root-cause analysis.

You do not need full packet capture everywhere to get value. Even periodic targeted captures, lab captures for baselining, and short-response captures during incidents can significantly improve defender understanding of normal and abnormal traffic.

The best way to learn Wireshark is to analyze normal traffic repeatedly: web browsing, DNS lookups, software updates, SSH sessions, API calls, and failed connections. Build a mental library of expected patterns before trying to identify malicious behavior.

Create a small personal filter set and refine it over time. Memorizing every protocol field is unnecessary. Instead, master a dependable workflow for filtering by host, protocol, stream, time, and error conditions.

Pair packet analysis with note-taking. Write short investigation summaries from lab captures. The act of translating packet details into clear evidence statements is exactly the skill you will need during real incidents.