According to Wikipedia https://en.wikipedia.org/wiki/Predatory_publishing:
Predatory publishing, sometimes called write-only publishing or deceptive publishing, is an exploitative academic publishing business model that involves charging publication fees to authors without checking articles for quality and legitimacy and without providing the other editorial and publishing services that legitimate academic journals provide, whether open access or not. They are regarded as predatory because scholars are tricked into publishing with them, although some authors may be aware that the journal is poor quality or even fraudulent. New scholars from developing countries are said to be especially at risk of being misled by predatory publishers.
How the scam works
According to a global network of researchers operating the website authoraid.info:
Questionable conferences can be hard to distinguish from reputable conferences—especially because they often have similar names. How can one know that a conference might be questionable? Perhaps be suspicious if the invitation does some of the following:
- asks you to speak even though the conference isn’t really in your field
- invites you to present research but doesn’t request an abstract
- emphasizes the beautiful location rather than the conference content
- lists fees that are much higher than usual in your field
- contains grammar errors, misspellings, or such
Some questionable conferences are held by companies that also publish questionable journals.
Finally, if you’re unsure whether a conference seems real and reputable, consider asking well-established scholars in your field.
More details can be found on https://www.authoraid.info/en/news/details/1156/.
The most cited source for such groups was Beall's List: https://en.wikipedia.org/wiki/Beall%27s_List. That list is no longer active, but is republished in various places online and constantly updated.
According to https://www.academia.edu/32424961/WHAT_ ... EY_OPERATE:
Credible journals do not chase authors and send article sub-mission invitations, rather authors look for them. However, legitimate publishers and journals also use email to reach potential authors on a regular basis. Authors should simply ignore or delete article submission invitations from questionable journals and publishers. Instead, they should only consider credible journals from well-established publishers. We have contacted Jeﬀrey Beall in case he would like to have the spam emails forwarded to him. He said
“I am always happy to have people forward me the spam emails they receive when they believe they have discovered a new questionable publisher or journal”.
He also stressed: before forwarding these emails, authors should ﬁrst check whether the name of the publisher or a journal is in the Beall’slist. Frequently, predatory publishers release new journals. Hence,authors should check whether these journals are included in the Beall’s list of predatory publishers.