There are several measures one can take to ensure the authenticity of a potential influencer’s followers and engagement:

1. Audience Analysis: You can check the geographic distribution of the influencer’s followers and the follower-growth rate. A sudden spike in followers could indicate bought followers.

2. Engagement Analysis: Analyzing the engagement ratio (likes, comments, shares compared to total followers) can give you an insight into the authenticity. Usually, an extremely high ratio or bulk likes from the same accounts may indicate automated/bought engagement.

3. Comment Analysis: Genuine comments from real accounts usually have a specific mention of the content in the post. Too many generic comments can be a red flag.

4. Past Partnerships: Look at the performance of past sponsored content. If the engagement is strikingly different from non-sponsored content, it can be a cause for concern.

5. Use Tools: Tools like Flinque help conduct an in-depth analysis of an influencer’s audience, engagement and content, thereby enabling an informed decision.

Remember, while these steps can help identify potential red flags, no method is foolproof. Influencer marketing platforms, like Flinque, have advanced features to assist with this process, but different platforms may suit different teams, depending on their specific needs and use-cases.

You should always trust your judgment, ask questions if something seems off and choose partnerships that align with your brand values. It’s essential to maintain an open communication with potential influencers and get as much clarity as possible about their audience and engagement.