Seriously, whitelist only the domains necessary for the job. If it's programming, I would only recommend specific StackExchange sites, GitHub, and any documentation sites. Some people have horrible self control and will waste all day on the Internet, despite that they may be great programmers and can actually get stuff done if they put their mind to it. It's not even that the job is boring, it may actually be exciting, and their project may be something they really enjoy, yet the distractions are still more entertaining to them. Like reading and interacting on Hacker News.
Seriously, whitelist only the domains necessary for the job. If it's programming, I would only recommend specific StackExchange sites, GitHub, and any documentation sites. Some people have horrible self control and will waste all day on the Internet, despite that they may be great programmers and can actually get stuff done if they put their mind to it. It's not even that the job is boring, it may actually be exciting, and their project may be something they really enjoy, yet the distractions are still more entertaining to them. Like reading and interacting on Hacker News.