Restricting affiliate codes to only work on specific customer segments is a great way to prevent affiliates from referring existing customers (and lots more). With this feature, you can include or exclude any segment of customers from using affiliate codes.
To set this up, head to your Programs tab and select the program you want to apply this to.
From within the program builder page, head to the Advanced Settings section. In the Discount codes apply to field, change All customers to Specific customer segments. An additional field will appear where you can select which customer segments you want the affiliate codes to work on.
To restrict code usage to new customers only, you can include a segment of customers who haven't purchased previously.
Click Save & Exit once done to set your changes live!