Predatory conferences appear legitimate, but use an exploitive business model similar to that of predatory publishers. Organisers exercise little or no editorial control over presentations and submitted papers. The involvement of prominent researchers is often claimed (usually without their knowledge) in an attempt to boost conference attendance numbers, if the conference exists at all.
Some aspects to look out for
Is the conference in your field or does it cover a broad range of subjects?
Does the conference appear to be a one-off event? Are the details and papers of the previous event available?
Who is organising the conference? Is there any connection to a legitimate research organization, professional society, or institute?
What sort of fees are associated with attending the conference? Are registration fees with accommodation, meals, and travel?
Do organisers claim that abstracts and papers will be peer reviewed or promise a fast review time, high acceptance rate?
Do organisers guarantee publication in a list of specified journals?
Academic Media Group (2019)