How to use the command 'snort' (with examples)

Snort is an open-source network intrusion detection system. It serves as a powerful tool for analyzing and detecting network traffic anomalies, attacks, and suspicious activities.

Use case 1: Capture packets with verbose output

Code:

sudo snort -v -i interface

Motivation: This use case is helpful when you need to capture network packets and obtain a detailed view of the captured data. The verbose output provides additional information about the packets, including network protocols, IP addresses, ports, and more.

Explanation:

• sudo: Executing Snort with superuser privileges (required for packet capturing).
• snort: The command itself.
• -v: Enables verbose output, providing detailed information about the captured packets.
• -i interface: Specifies the network interface (e.g., eth0) to capture packets from.

Example output:

TCP src: 192.168.0.1:12345 -> dest: 192.168.0.2:80
UDP src: 192.168.0.3:54321 -> dest: 192.168.0.4:53

Use case 2: Capture packets and dump application layer data with verbose output

Code:

sudo snort -vd -i interface

Motivation: This use case is useful when you need to not only capture network packets but also analyze the application layer data within those packets. It allows for a deeper inspection of the payload and can be handy for debugging network applications or identifying potential threats.

Explanation:

• -d: Enables dumping of application layer data for captured packets, such as HTTP requests and responses.
• Other arguments are the same as in Use case 1.

Example output:

TCP src: 192.168.0.5:12345 -> dest: 192.168.0.6:80
GET /index.html HTTP/1.1
...

Use case 3: Capture packets and display link layer packet headers with verbose output

Code:

sudo snort -ve -i interface

Motivation: This use case is helpful for capturing network packets and obtaining detailed information about the link layer headers, such as Ethernet addresses, MAC addresses, frame types, etc. It allows for a comprehensive analysis of network traffic at a lower network layer.

Explanation:

• -e: Displays link layer packet headers for captured packets.
• Other arguments are the same as in Use case 1.

Example output:

TCP src: 192.168.0.7:12345 -> dest: 192.168.0.8:80
Ethernet: src: 00:11:22:33:44:55, dest: AA:BB:CC:DD:EE:FF, type: IPv4

Use case 4: Capture packets and save them in the specified directory

Code:

sudo snort -i interface -l path/to/directory

Motivation: This use case is useful when you want to capture network packets and save them for later analysis. By specifying the output directory, you can easily organize and access the captured packets at a later time.

Explanation:

• -l: Specifies the output directory to save the captured packets.
• Other arguments are the same as in Use case 1.

Example output: (Packets saved in the specified directory.)

Use case 5: Capture packets according to rules and save offending packets along with alerts

Code:

sudo snort -i interface -c path/to/rules.conf -l path/to/directory

Motivation: This use case is crucial when you want to perform intrusion detection by capturing packets based on pre-defined rules. Snort allows the configuration of rules to match certain network traffic patterns or suspicious activities. Capturing and saving offending packets along with alerts enables further analysis or investigation.

Explanation:

• -c path/to/rules.conf: Specifies the path to the rules configuration file.
• Other arguments are the same as in Use case 4.

Example output: (Offending packets saved in the specified directory along with alerts.)

Conclusion:

Snort is a versatile command for capturing and analyzing network packets. By using different arguments and options, you can customize the packet capturing process and obtain detailed information about the packets or application layer data. Additionally, Snort’s rule-based approach enables advanced intrusion detection capabilities. Familiarity with these use cases will empower you to effectively monitor and secure your network traffic.