For spam filtering, whitelists and blacklists are generally used as regular DNS lookups. However, for high-traffic sites, DNS lookups are not the preferred method, as this may lead to certain (small) delays for message delivery.
Alternatively, most DNSWL and DNSBL providers offer downloads of their data in different formats (sometimes for a fee). While it is technically possible to handle this download outside of the Notes environment and fully transparent, it would be beneficial in some situations to have the server either use a downloaded file directly and/or even initiate the download from within.
Disclosure: I'm responsible for the dnswl.org project, and as such have an interest to make Notes environments well-behaved out of the box.