Normally, finishing a sales is good. But if the customer is likely to ask for a refund, or when he/she is known for spamming shops, you might want to prevent the sales from ever happening. This extension allows you to create simple rules that prevent a customer from ever reaching the checkout, whenever that customer is matched with the rule. The rule might include multiple email-addresses (either complete email-addresses or partial email-words) or multiple IP-addresses. A customer that is denied sales is redirected towards a page displaying a CMS-page of your choice instead.
Please note that this extension is only available under Magento 1 (which is by now a deprecated platform that you should move away from). We have released a new extension for Magento 2, which is listed on our extensions page.