How to sew up a copyright link on a customer's website with a dependency?

Question

Copyright

Actually, it is necessary to somehow sew up a link (copyright) on the customer's website.
It turns out that we created a site, placed a copyright in the footer, and after a while the customer simply deletes the link.
There are some methods or ways to do this so that when this link / text / picture is deleted, the site breaks or some kind of inscription constantly pops up.
The methods are also interesting when part of the information is picked up from our site (so that there is a dependence).
Thank you!
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ps sites on php, wordpress, joomla and others.

Answer 1

Agreement with the customer. Add a requirement for mandatory placement of a link and penalties for violation.

Answer 2

Doesn't the customer have full rights to their own site? I think he has and he can do anything with his site.

Answer 3

Greetings! It is really possible to implement this in practice, and there are a lot of options for the so-called "diploit", limited only by the imagination of the programmer. But there are a couple of things:
1. It’s unlikely that anyone will earn you a diploma for free
2. When contacting a more or less competent specialist, he will be dropped anyway (but money and nerves will undoubtedly suffer)