Snort- a popular open-source IDS/IPS

Situatie

Snort is a powerful, open-source network intrusion detection and prevention system (IDS/IPS) used to monitor network traffic and detect malicious activity such as exploits, malware, and unauthorized access. It works by analyzing network packets and comparing them to predefined rules.

Solutie

Installing Snort

a) For Linux (Ubuntu/Debian)

Update the package list:

sudo apt-get update

Install Snort:

sudo apt-get install snort

b) For CentOS/RHEL

Install Snort via EPEL:

sudo yum install snort

c) For macOS

Install using Homebrew:

brew install snort

d) For Windows

Download the Windows version from the Snort website: Snort Downloads.
Follow the installation instructions.

Basic Configuration of Snort

1.Edit Snort Configuration File: The main configuration file is located at /etc/snort/snort.conf (Linux).

You may need to specify your network interface, home network settings, and other parameters.

Example:

var HOME_NET [192.168.1.0/24]
var EXTERNAL_NET !$HOME_NET

2.Set up Rule Paths: In the snort.conf file, specify the path to the rule sets.

include $RULE_PATH/local.rules

3.Download and Update Snort Rules: Snort requires rule sets to detect specific threats. These can be downloaded from Snort.org or updated via the command:

Running Snort

a) Basic IDS Mode (Packet Sniffer)

To run Snort in packet-sniffing mode, use the following command:

sudo snort -A console -c /etc/snort/snort.conf -i eth0

-“A console”: Outputs alerts to the console.

-“c /etc/snort/snort.conf”: Specifies the configuration file.

-“i eth0”: Specifies the network interface to monitor (replace eth0 with your network interface name).

b) IDS/IPS Inline Mode (Prevention)

To run Snort as an IPS (Intrusion Prevention System) to block malicious traffic, use the following command:

sudo snort -Q -c /etc/snort/snort.conf -i eth0

-Q: Enables inline mode for blocking attacks.

Snort Rules

Snort uses a set of rules to detect and respond to network activity. Rules are defined in the .rules files and consist of conditions to identify malicious activity.

Basic rule format:

-alert tcp any any -> any 80 (msg:”Possible SQL Injection”; content:”union select”; sid:1000001;)

-alert: Action to take (e.g., alert, log, drop).

-tcp: Protocol being monitored.

-any any: Source and destination IP addresses/ports.

-content: The string or pattern to look for.

-sid: The unique Snort ID for the rule.

Viewing Snort Alerts

Snort generates alerts in the format specified by the -A option. For example, if you run Snort with the -A console option, alerts will display in the terminal.

To view logged alerts from Snort, check the default alert log file:

/var/log/snort/alert

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