Protecting controller action access

[eluser]davidMC1982[/eluser]
I have a controller method/function/action that produces a CSV file of certain database records. What would be the best way to limit access to this function?

I don't want to use authentication on the site itself, but could use a DB table of allowed URL's or IP's or similar. htaccess would be another option. There's no real data/security issue as it's only data that could be scraped directly from the site anyway.

An external server will be downloading the CSV.

Thanks,

David