there are many different cloud-based services, which can do the real-time check of you traffic and stop the bad bots. It depends on what exactly you need. You can easily find an option. For example you can take a look at the https://botguard.net, maybe it can help.
A disclaimer: I am working at BotGuard – service which can protect your website from malicious bots, crawlers, scrapers, and hacker attacks. And you can get started with BotGuard for free.