I use /etc/hosts. I made /etc/hosts.default and /etc/hosts.work. At 10:00 `cron` (with sudo) lauches `cp` to copy /etc/hosts.work over /etc/hosts. At 18:00 /etc/hosts.default is copied over.

The /etc/hosts.work file contains a list of websites I don’t want to check during work. But HN is not in this list, yet.