A problem with this approach was that many readers use VPN’s and other proxies that change IP addresses virtually every time they use them. For that reason and because I believe in protecting every Internet user’s privacy as much as possible, I wanted a way of immediately unblocking visitors to my website without them having to reveal personal information like names and email addresses.
I recently spent a few weeks on a new idea for solving this problem. With some help from two knowledgeable users on Blue Dwarf, I came up with a workable approach two weeks ago. So far, it looks like it works well enough. To summarize this method, when a blocked visitor reaches my custom 403 error page, he is asked whether he would like to be unblocked by having his IP address added to the website’s white list. If he follows that hypertext link, he is sent to the robot test page. If he answers the robot test question correctly, his IP address is automatically added to the white list. He doesn’t need to enter it or even know what it is. If he fails the test, he is told to click on the back button in his browser and try again. After he has passed the robot test, Nginx is commanded to reload its configuration file (PHP command: shell_exec(“sudo nginx -s reload”);), which causes it to immediately accept the new whitelist entry, and he is granted immediate access. He is then allowed to visit cheapskatesguide as often as he likes for as long as he continues to use the same IP address. If he switches IP addresses in the future, he has about a one in twenty chance of needing to pass the robot test again each time he switches IP addresses. My hope is that visitors who use proxies will only have to pass the test a few times a year. As the whitelist grows, I suppose that frequency may decrease. Of course, it will reach a non-zero equilibrium point that depends on the churn in the IP addresses being used by commercial web-hosting companies. In a few years, I may have a better idea of where that equilibrium point is.
I believe using a CDN would defeat the author’s goal of not being reliant on third-party service providers.