If your Zen Cart website has a ‘contact form’, which collects visitor information, be aware that spammer’s software commonly uses this feature to send unwanted emails. The solution to stopping these emails is straightforward and effective: Have your webmaster install a CAPTCHA on your ‘form’.
What is a CAPTCHA? A CAPTCHA is an acronym for “Completely Automated Public Turing test to tell Computers and Humans Apart”. CAPTCHA’s are used to prevent automated software from using your form to send spam emails. A CAPTCHA generally uses a graphic image of random letters and numerals in lower and upper case.
Example 1: 
Example 2: 
The viewer needs to type in the random password correctly to submit the form. The test ensures that a computer cannot generate the correct response, as computers cannot ‘read’ the graphic image password. Because other computers are unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human.
A commonly targeted weakness of zen-cart websites is spam emails being sent through the websites using the “Tell a Friend” form. If the spam emails get too frequent your site may be suspended by the hosting service and need to be reinstated. If you feel like you’ve been having the same issue, here is a way to solve the problem by allowing only “logged-in” customers to use the Tell a Friend form.
