Contact forms are a standard feature on most websites that are often abused by spammers. There are several known methods of reducing the number of unwanted messages received from a contact form including CAPTCHAs, third-party spam filtering services or backend solutions relying on black-lists and spam detectors. CAPTCHA is usually the worst choice as it totally destroys the user experience. The other options could be viable if you run a website with a large audience. For small resources like this blog they are an overkill.