How do you use network forensics tools to monitor and capture malicious traffic and packets?

To perform network forensics and detect malicious activities: Understand the network layout and assets. Choose appropriate tools like Wireshark, Tcpdump, and SIEM solutions. Deploy monitoring systems and capture packets with specified filters. Analyze captured packets for anomalies and malicious behavior. Leverage tools like Zeek for detailed traffic analysis. Correlate network logs with other sources for a comprehensive view. Document findings, including IoCs, and take remediation actions. Integrate network forensics into an overall incident response plan while adhering to legal and ethical considerations.

Malicious traffic and packets refer to data transmitted over a network that is intended to harm, exploit, or otherwise negatively impact systems or data. Examples include malware communications, unauthorized data exfiltration, and distributed denial-of-service (DDoS) attacks. For instance, a packet containing ransomware payloads would be considered malicious as it aims to encrypt files and demand a ransom for decryption.

Take into consideration that different tools will collect and analyze different type and size of artifacts. Depending on how much data you can afford to store and what you can analyze at scale, you could prefer to run tools in order to store Full Packet Captures, only segments of Network connections (maybe only the ones matching a specific rule) or even only network metadata (such as Zeek or Netflow). Finally, one could decide to save a combination of those for multiple purposes. This decision can drastically change you forensics capabilities and should be carefully determined up front.

Network forensics tools are specialized software and hardware used to monitor, capture, analyze, and investigate network traffic to detect and respond to security incidents. Examples include Wireshark, which captures and analyzes packet data, and Snort, which acts as an intrusion detection system. These tools help security professionals identify and mitigate malicious activities.

Wireshark: A widely-used network protocol analyzer that captures and displays packets in real-time. Zeek (formerly Bro): An open-source network monitoring framework that provides detailed traffic analysis and logging. Snort/Suricata: Network intrusion detection/prevention systems (IDS/IPS) that analyze real-time traffic for suspicious patterns. NetFlow/IPFIX: Flow data collection protocols used by tools like SolarWinds NetFlow Traffic Analyzer to monitor network traffic patterns.

Network topologies can be very complex, and a careful plan should be done to find which network interface attach to in order to collect traffic. Ideally, one wants to collect traffic from all over the network to have full visibility during an Incident investigation, but this is not always easily achievable and the best compromise should be chosen in order to achieve desired goals.

Monitoring network traffic involves using tools to continuously observe data flow across the network. This can be done using network taps, span ports, or inline devices. For example, setting up a network monitoring tool like SolarWinds Network Performance Monitor helps administrators visualize traffic patterns and detect anomalies that may indicate malicious activity.

In addition to looking for Indicator of Compromise, behavior based analysis should be considered to search for attacker Techniques (see Mitre ATT&CK for reference) and environment anomalies, which permit a higher coverage and visibility on potential threats.

Capturing malicious traffic involves using packet capture tools to intercept and record network data for analysis. Tools like Wireshark or tcpdump can capture all traffic on a network segment, allowing analysts to filter and isolate suspicious packets. For instance, during a suspected breach, capturing packets can reveal the attacker's IP address and the methods used to infiltrate the network.

Analyzing malicious traffic involves examining captured data to identify and understand threats. This can include decoding protocols, inspecting payloads, and correlating events. For example, using Wireshark, an analyst can reconstruct a malicious email attachment that was exfiltrated, revealing how the attacker compromised the network and what data was accessed.

Presenting evidence requires organizing and documenting findings in a clear, understandable manner for stakeholders such as management or legal teams. This includes detailed reports, visualizations of attack vectors, and timelines of events. For example, using reporting features in tools like Splunk can help create comprehensive incident reports that summarize the attack and the response actions taken.

Beyond the basics, consider integrating network forensics with other security measures like endpoint detection and response (EDR) and threat intelligence feeds. Additionally, implementing continuous monitoring and automated alerting can help quickly identify and respond to new threats. For instance, using an automated system to flag unusual network behavior in real-time can significantly reduce the time it takes to detect and mitigate an attack.