Services like TrueTwit might help. Users get a message in Twitter inbox to verify that they are not bots and have to solve a captcha on TrueTwit. Not sure about how accurately this works – in case bots are able to solve captcha? But I don’t think anyone would invest so much in a bot to do that.
Downside ? Using services like TrueTwit comes at a cost – losing those real human followers who do not notice the message they get on your behalf.
If I am interpreting the statistics (see below) provided by TrueTwit correctly, ~50% have verified the accounts, so are real human followers.
Total Followers
27,544,255
Verified Followers
13,032,338
How many of the remaining ~50% are real bots ? If we go by their current mechanism, I don’t think even TrueTwit can answer that.
So, I would take this approach –
- If getting hundreds of followers per day, use TrueTwit (or similar service)
- Periodically review those followers who have not yet verified manually and filter the bots. We can say from above stats, you will reduce workload at least by half.
- Else, if getting only a few followers per day, just review manually.
- If time is an issue, in either case where manual review is required hire someone from freelancing services like upwork to do the task – you will need to grant access to the freelancer – so take care about how to manage access.