# /etc/snort

The `/etc/snort` directory is a crucial part of a Snort installation, housing the configuration files, rules, and other necessary resources for running Snort effectively. Here's an overview of the important files and directories typically found in `/etc/snort`:

### Overview of `/etc/snort`

1. **snort.conf**:
   * **Description**: The main configuration file for Snort.
   * **Purpose**: Defines the global settings, paths to rules, preprocessors, output plugins, and other operational parameters for Snort.
   * **Location**: `/etc/snort/snort.conf`
   *   **Example**:

       ```shell
       var HOME_NET 192.168.1.0/24
       var EXTERNAL_NET any

       include $RULE_PATH/local.rules
       include $RULE_PATH/community.rules
       include $RULE_PATH/snort.rules
       ```
2. **rules/**:
   * **Description**: Directory containing the rule files used by Snort.
   * **Purpose**: Houses predefined rule sets and custom rules for detecting various types of network traffic anomalies and threats.
   * **Location**: `/etc/snort/rules/`
   * **Common Files**:
     * `local.rules`: Custom rules defined by the administrator.
     * `snort.rules`: Official Snort rules.
     * `emerging.rules`: Rules from Emerging Threats or other sources.
3. **classification.config**:
   * **Description**: Defines how alerts are classified and prioritized.
   * **Purpose**: Maps alert signatures to human-readable descriptions and assigns priorities to different types of alerts.
   * **Location**: `/etc/snort/classification.config`
   *   **Example**:

       ```shell
       config classification: attempted-admin,Attempted Administrator Privilege Gain,1
       config classification: attempted-user,Attempted User Privilege Gain,2
       ```
4. **reference.config**:
   * **Description**: Maps Snort rule references to external security resources.
   * **Purpose**: Provides links to external documentation and resources related to specific alerts.
   * **Location**: `/etc/snort/reference.config`
   *   **Example**:

       ```shell
       config reference: bugtraq https://www.securityfocus.com/bid/
       config reference: cve https://cve.mitre.org/cgi-bin/cvename.cgi?name=
       ```
5. **sid-msg.map**:
   * **Description**: Maps Snort rule IDs (SIDs) to alert messages and references.
   * **Purpose**: Ensures that alerts generated by Snort have meaningful messages and references.
   * **Location**: `/etc/snort/sid-msg.map`
   *   **Example**:

       ```shell
       1000001 || ICMP PING NMAP || cve,CAN-1999-0524 || url,www.securityfocus.com/bid/277
       ```
6. **threshold.conf**:
   * **Description**: Defines thresholding and suppression rules.
   * **Purpose**: Controls how frequently alerts are generated for specific rules to reduce noise and false positives.
   * **Location**: `/etc/snort/threshold.conf`
   *   **Example**:

       ```shell
       threshold gen_id 1, sig_id 1000001, type threshold, track by_src, count 5, seconds 60
       ```
7. **snort\_debian.conf** (specific to Debian-based systems):
   * **Description**: Contains settings for running Snort as a service.
   * **Purpose**: Defines variables used by the Snort init script, such as the interface to listen on and additional command-line options.
   * **Location**: `/etc/snort/snort_debian.conf`
   *   **Example**:

       ```shell
       DEBIAN_SNORT_STARTUP="yes"
       INTERFACE="eth0"
       ```
8. **preproc\_rules/**:
   * **Description**: Directory containing rules for preprocessors.
   * **Purpose**: Houses rules that are applied by Snort preprocessors to detect protocol-specific anomalies and other pre-processing tasks.
   * **Location**: `/etc/snort/preproc_rules/`

### Example Directory Structure

```
/etc/snort/
├── classification.config
├── reference.config
├── sid-msg.map
├── snort.conf
├── snort_debian.conf
├── threshold.conf
├── rules/
│   ├── local.rules
│   ├── snort.rules
│   ├── emerging.rules
│   └── ...
├── preproc_rules/
│   ├── preprocessor.rules
│   └── ...
```

### Best Practices

1. **Regular Updates**: Regularly update Snort rules and configurations to stay protected against new threats.
2. **Custom Rules**: Create and maintain custom rules in `local.rules` to address specific needs or threats unique to your environment.
3. **Rule Optimization**: Review and optimize rules to reduce false positives and improve detection accuracy.
4. **Backup Configurations**: Keep backups of your configuration files to quickly recover from misconfigurations or system failures.
5. **Secure Access**: Ensure that the `/etc/snort` directory and its contents are securely accessible only to authorized users to prevent tampering.

By understanding and properly configuring the files within `/etc/snort`, administrators can effectively leverage Snort's capabilities to protect their networks from a wide range of threats.
