Adding a Captcha to contact form.

I’ve been using a theme for a while which has since been removed from ThemeForest, so I can’t request support from the theme’s author.

The contact form was built-in as part of the theme, would it be possible to add a captcha field to the existing form?

I’ve had a big surge of spam recently, alongside plenty of genuine emails, so I’m keen to combat these without losing the styling or genuine contact requests.