How to block a user? [duplicate]

Question

I want to create a php script which blocks a user and not a whole network(modem). I know i can get the IP from the modem, but how can my server differentiate the user behind the modem? Is there a possible solution?

Answer 1

There is no way just to block one user: You could block the combination of user agent and IP address, but the user could change the browser. A hacker could change his user agent as well so far almost not possible.

Things you could try (but they may fail):

• Block the combination of User-Agent and IP
• Set a block cookie
• Set a block entry in the local storage
• Create a fingerprint based e.g. on the installed plugins or fonts

Answer 2

When user is clever enough to know how to clean cookies, it's not possible to do what you want without blocking IP.