Migrate from Snort 2 to Snort 3 In Secure Firewall Management Center

Migrate from Snort 2 to Snort 3

Snort is an intrusion detection and prevention system that has undergone a significant change from Version 2 to Version 3. To leverage the enhanced features and capabilities of Snort 3, migration of the existing rule sets from Snort 2 becomes crucial. This migration process involves converting and adapting the Snort 2 rules to the Snort 3 rule syntax and optimizing them for improved detection and performance.

In some cases, organizations can have the threat defense devices managed by the Secure Firewall Management Center. Organizations can opt for a hybrid deployment approach during the migration from Snort 2 to Snort 3. This approach allows for a gradual transition and minimizes potential disruptions, if any.

Benefits of Migrating to Snort 3

  • Enhanced protocol support—Snort 3 provides improved protocol support, allowing you to monitor and detect threats across a wide range of modern protocols, including encrypted traffic.
  • Streamlined rule management—Snort 3 offers a more user-friendly rule language and rule management system, making it easier to create, modify, and manage rules effectively.
  • Improved performance—Snort 3 has been optimized to handle higher traffic volumes more efficiently, reducing the risk of performance bottlenecks and ensuring timely threat detection.

Sample Business Scenario

Alice works as a security analyst in a large organization that heavily relies on the Snort inspection engine to monitor and protect their network infrastructure. The organization has been using Snort Version 2 for several years, but they have encountered some limitations and challenges.

Bob, the network administrator, is looking to migrate from Snort 2 to Snort 3 to overcome these issues and enhance his organization's network security capabilities.

This migration will also improve network security monitoring, enhance performance, and streamline rule management.

Best Practices for Migrating from Snort 2 to Snort 3

Enable Snort 3 on Threat Defense


Attention
During the deployment process, there could be a momentary traffic loss because the current inspection engine needs to be shut down.

Procedure

Step 1

Choose Devices > Device Management.

Step 2

Click the corresponding device to go to the device home page.

Step 3

Click the Device tab.

Step 4

In the Inspection Engine section, click Upgrade.

Step 5

Click Yes.

What to do next

Deploy the changes on the device. See Deploy Configuration Changes.

The system converts your policy configurations during the deployment process to make them compatible with the selected Snort version.

Convert Snort 2 Rules of a Single Intrusion Policy to Snort 3

Procedure

Step 1

Choose Policies > Intrusion.

Step 2

In the Intrusion Policies tab, click Show Snort 3 Sync status.

If your policy displays an orange arrow, it indicates that the Snort 2 and the Snort 3 versions of the intrusion policy are not synchronized.

Step 3

Click the orange arrow.

The Snort 2 to Snort 3 Sync Summary page displays that the Snort 2 to Snort 3 sync is pending.

Step 4

Click Re-Sync to start the synchronization.

Note

 
When you click Re-Sync, the snort2Lua tool converts the rules from Snort 2 to Snort 3.

The Summary Details section lists the rules that were migrated or skipped. In our use case, there are 76 custom Snort 2 rules, 17 rules with thresholds, and 15 rules with suppression that were skipped during the sync process. To migrate the custom rules, go to the next step.

To migrate rules with thresholds and suppressions, go to Step 6.

Step 5

To migrate the 76 custom rules, perform either one of these steps:

  • In the Custom Rules tab, click the Import icon to convert and auto-import the local rules to the Snort 3 version of the policy.

    A confirmation message is displayed after the rules are successfully imported.

  • Choose Objects > Intrusion Rules and click Snort 3 All Rules.

    1. Click Local Rules in the left panel to check if any rules have been migrated. Notice that no custom rules from Snort 2 have been migrated.

    2. From the Tasks drop-down list, choose Convert Snort 2 rules and import.

    3. Click OK.

      A newly created rule group (All Snort 2 Converted Global) is created under Local Rules in the left panel.

      Notice that all 76 custom rules have been migrated, as shown in the following figure.

    Alternatively, you can select the Convert Snort 2 rules and download in the previous step to save the rules file locally. You can review the converted rules in the downloaded file and later upload them using the Upload Snort 3 rules option.

Step 6

Click the Download Summary Details link to download the rules in .txt format.

The following is a sample of the summary that is displayed.

  "id": "00505691-15DC-0ed3-0000-004294988561",
  "name": "_Intrusion_Policy_1",
  "type": "IntrusionPolicy",
  "syncStatus": {
    "source": {
      "id": "bdce2d6a-1ebe-11ee-8e88-220032eb1fb5",
      "type": "IntrusionPolicy"
    },
    "status": "WARN",
    "description": "Migration is partially successful. Some of the rules are not copied to Snort3.",
    "timestamp": 1690883954814,
    "lastUser": {
      "name": "admin"
    },
    "details": [
      {
        "type": "Summary",
        "status": "INFO",
        "description": "Based on Talos rule-mapping 18639 Snort 2 rule action overrides migrated to 18635 Snort 3 rules."
      },
      {
        "id": "1:1000156=alert,1:1000114=alert,1:1000160=alert,1:1000135=alert,1:1000115=alert,1:1000118=alert,
         1:1000092=alert,1:1000139=alert,1:1000123=alert,1:1000159=alert,1:1000149=disabled,1:1000167=alert,
         1:1000133=alert,1:1000095=alert,1:1000143=alert,1:1000106=alert,1:1000153=alert,1:1000097=alert,1:1000141=alert,
         1:1000148=alert,1:1000090=alert,1:1000119=alert,1:1000112=alert,1:1000138=alert,1:1000128=alert,1:1000132=alert,
         1:1000134=alert,1:1000145=disabled,1:1000110=disabled,1:1000107=alert,1:1000163=alert,1:1000124=alert,1:1000125=alert,
         1:1000094=alert,1:1000113=disabled,1:1000147=alert,1:1000161=alert,1:1000105=disabled,1:1000140=alert,1:1000111=alert,
         1:1000102=alert,1:1000129=disabled,1:1000108=alert,1:1000144=disabled,1:1000088=alert,1:1000091=alert,1:1000131=alert,
         1:1000157=alert,1:1000120=alert,1:1000126=alert,1:1000165=alert,1:1000146=alert,1:1000162=alert,1:1000116=alert,1:1000142=alert,
         1:1000170=disabled,1:1000169=alert,1:1000104=alert,1:1000099=disabled,1:1000171=alert,1:1000093=alert,1:1000087=alert,1:1000100=alert,
         1:1000137=alert,1:1000158=alert,1:1000103=alert,1:1000098=alert,1:1000127=disabled,1:1000130=alert,1:1000164=alert,1:1000089=alert,
         1:1000109=alert,1:1000136=alert,1:1000117=alert,1:1000166=alert,1:1000168=alert",
        "type": "PolicyInfo",
        "description": "Corresponding Snort 2 policy overridden custom (local) rules."
      },
      {
        "type": "AssignedDevices",
        "status": "INFO",
        "description": "Snort3:0 , Snort2:0"
      },
      {
        "id": "122:6",
        "type": "Threshold",
        "status": "ERROR",
        "description": "PSNG_TCP_FILTERED_DECOY_PORTSCAN"
      },
      {
        "id": "122:15",
        "type": "Threshold",
        "status": "ERROR",
        "description": "PSNG_IP_PORTSWEEP_FILTERED"
       },
      {
        "id": "122:1",
        "type": "Threshold",
        "status": "ERROR",
        "description": "PSNG_TCP_PORTSCAN"
      },

Step 7

Click Close to close the Sync Summary dialog box.

Step 8

To check the rules with status: ERROR, choose Policies > Intrusion and click the Snort 2 version of the intrusion policy.

Step 9

Under Policy Information, click Rules and filter for the rule. For example, enter PSNG_TCP_PORTSCAN in the Filterfield to find the rule.

Step 10

Click Show Details to view the detailed version of the rule.

Step 11

Create the rule again in Snort 3 using Snort 3 rule guidelines and save the file as a .txt or .rules file. For more information, see www.snort3.org.

Step 12

Upload the custom rule that you just created locally to the list of all the Snort 3 rules. See Add Custom Rules to Rule Groups.

What to do next

Deploy configuration changes. See Deploy Configuration Changes.

Deploy Configuration Changes

After you change configurations, deploy them to the affected devices.


Note

This topic covers the basic steps involved in deploying configuration changes. We strongly recommend that you refer the Deploy Configuration Changes topic in the latest version of the Cisco Secure Firewall Management Center Configuration Guide to understand the prerequisites and implications of deploying the changes before proceeding with the steps.


Caution
When you deploy, resource demands may result in a small number of packets dropping without inspection. Additionally, deploying some configurations restarts the Snort process, which interrupts traffic inspection. Whether traffic drops during this interruption or passes without further inspection depends on how the target device handles traffic.

Procedure

Step 1

On the Secure Firewall Management Center menu bar, click Deploy and choose Deployment.

The GUI page lists the devices with out-of-date configurations having Pendingstatus.

  • The Modified By column lists the users who have modified the policies or objects. Expand the device listing to view the users who have modified the policies for each policy listing.

    Note

     

    Usernames are not provided for deleted policies and objects.

  • The Inspect Interruption column indicates if traffic inspection interruption might occur in the device during deployment.

    If this column is blank for a device, it indicates that there will be no traffic inspection interruptions on that device during deployment.

  • The Last Modified Time column specifies the last time you made configuration changes.

  • The Preview column allows you to preview the changes for the next deployment.

  • The Status column provides the status for each deployment.

Step 2

Identify and choose the devices on which you want to deploy configuration changes.

  • Search—Search for the device name, type, domain, group, or status in the search box.
  • Expand—Click Expand Arrow (expand arrow icon) to view device-specific configuration changes to be deployed.

    When you check a check box adjacent to a device, all the changes made to the device and listed under the device, are pushed for deployment. However, you can use Policy selection (policy selection icon) to select individual policies or specific configurations to deploy while withholding the remaining changes without deploying them.

    Note

     

    • When the status in the Inspect Interruption column indicates (Yes) that deploying will interrupt inspection, and perhaps traffic, on a threat defense device, the expanded list indicates the specific configurations causing the interruption with the Inspect Interruption (inspect interruption icon).

    • When there are changes to interface groups, security zones, or objects, the impacted devices are shown as out-of-date on the management center. To ensure that these changes take effect, the policies with these interface groups, security zones, or objects, also need to be deployed along with these changes. The impacted policies are shown as out-of-date on the Previewpage on the management center.

Step 3

Click Deploy.

Step 4

If the system identifies errors or warnings in the changes to be deployed, it displays them in the Validation Messages window. To view complete details, click the arrow icon before the warnings or errors.

You have the following choices:

  • Deploy—Continue deploying without resolving warning conditions. You cannot proceed if the system identifies errors.
  • Close—Exit without deploying. Resolve the error and warning conditions, and attempt to deploy the configuration again.

What to do next

During deployment, if there is a deployment failure, there is a possibility that the failure may impact traffic. However, it depends on certain conditions. If there are specific configuration changes in the deployment, the deployment failure may lead to traffic being interrupted. For details, see the Deploy Configuration Changes topic in the latest version of the Cisco Secure Firewall Management Center Configuration Guide.