Look for something that says Add exception or maybe Manage exceptions.
It should be somewhere in the antivirus settings.
Here... I found it... this is for Norton 360.
Here's the link to the PDF...
Norton 360 User Manual (PDF)
Set SONAR to remove threats automatically
1 Start Norton.
If you see the My Norton window, next to Device Security, click Open.
2 In the Norton main window, click Settings.
3 In the Settings window, click Antivirus.
4 Under Remove Risks Automatically, set the slider to Always.
5 Under Remove Risks if I Am Away, set the slider to Always.
6 Click Apply.
In the section below, you want to set the AV to "exclude" the Mozilla Firefox folder, located here...
C:\Program Files\Mozilla Firefox
Set Auto-Protect to exclude known good files from Norton scans
If you think Norton identifies a valid application as a security risk, you can exclude the file from
Norton scans.
Exclude files from Norton scans
1 Start Norton.
If you see the My Norton window, next to Device Security, click Open.
2 In the Norton main window, click Settings.
3 In the Settings window, click Antivirus.
4 In the Antivirus settings window, click the Scans and Risks tab.
5 Under Exclusions / Low Risks, do one of the following:
6 In the window that appears, click Add Folders or Add Files.
7 In the Add Item dialog box, click the browse icon. In the dialog box that appears, select
the item that you want to exclude from scans.
8 Click OK.
