This
i have a simple php form
in combination with this
i am not to clued up on php
May have some serious hidden consequences you don't know about. To (re-answer, add to) answer the Q, spammers are paid on delivery, they don't care about the link content.
When you say "simple php script," what worries me is it may be vulnerable to injection. What this means is you receive a single email, but the it's possible it's being abused to send thousands of emails to other targets. A typical example, if I can inject something like this into the "email address" field
from: blah@example.com\n
bcc:email1@example.com, email2@example.com,email3@example.com I've just sent out three emails you don't know about, and will never, as I've created my own BCC field. The above example won't "work" in a regular form, there are special tricks that need to be done, but that is the concept.
I've got tons of posts here with suggestions, and there are more from others, but resort to CAPTCHA as just that, a last resort. IMO it is an unnecessary barrier to your users and there are **many** ways to put a stop to link-drop spam in particular.
Square one is to log all input data so you know what they are up to, two cleanse your input, three, after these, kill malicious patterns and don't send email - if you take away their toys, they will lose interest in you. Have someone review this script for security issues, just in case.
