Open Access journals with article processing charges (APCs) are an attempt to change the way scholarly journals work, allowing authors or their institutions to pay once the article had been peer reviewed and accepted. The move away from subscriptions would allow anyone in the world to freely read the scholarship presented.
This business model, linked with the ability to create professional-looking web pages cheaply, gave scammers an opportunity. They create a fake journal website, solicit articles from researchers via email, accept those articles immediately without any peer review, collect the APC, and post the article. Fake conferences also follow this model.
There is no standard definition for 'predatory journal'. These journals often share characteristics with new or low-quality journals. In 2019 a groups of researchers and publishers proposed a definition and list of characteristics in this Nature article, Predatory Journals: No Definition, No Defence. They want their work to be discussed. They have a website where they'll gather data and information. A 2020 blog post, There is no black and white definition of predatory publishing by Kyle Siler, is based on his research demonstrating the range of behaviors lumped under this term.
Finding Reliable Open Access Journals and Books
Since identifying a predatory journal is a process and involves a lot of subjective considerations, there isn't one list of bad actors. You should use one or more of the sites below to help you identify predatory journals. Most of these are 'white lists', or lists of journals that meet certain requirements to prove they are reputable. Some are lists of characteristics for you to look for when considering a journal.