Please read through the links below:

https://www.google.com/amp/s/publons.com/blog/hijacked-journals-what-they-are-and-how-to-avoid-them/amp/

https://en.m.wikipedia.org/wiki/Predatory_publishing

Heshu - not quite sure what you mean by 'hijacked journals?'

Please read through the links below:

https://www.google.com/amp/s/publons.com/blog/hijacked-journals-what-they-are-and-how-to-avoid-them/amp/

https://en.m.wikipedia.org/wiki/Predatory_publishing

Borrowing from researcher César Jiménez-Yanez:

Regularly predatory journals have the following characteristics:

• Send emails regularly inviting to publish
• They offer impact factor and show medals and high indicators
• Offer to publish in a very short time (days or weeks)
• They are multidisciplinary, that is, they accept jobs from all areas and disciplines.
• Charge to be published (high costs)
• They do not detail the arbitration process (sometimes they do not even mention it)
• Present the DOI or Crossref logo as something "important"
• The name of the magazine regularly looks like a serious academic journal
• They are not affiliated with COPE (https://publicationethics.org/)

Anton Vrdoljak Kudos!. The only addition (or little correction to your item No5) from my own angle is the cost. They sometimes charge affordably reduced cost and are open to reduction on bargaining, similar to buying common food items in the market, during negotiation. They are predominantly from India. They disturb a lot, with frivolous messages through the email.

@dean whitehead

Hijacked journals are duplicate or fake websites of legitimate ones utilizing the title, ISSN and other information of the reputable journal. They are often created by a malicious third party for the purpose of fraudulently offering academicians the opportunity to rapidly publish their research online for a fee.

Dear Heshu,

They are all predatory journals. However, hijacked journals use the titles of already known peer-reviewed journals to attract researchers so when searching you can realize that it is indexed! but in fact, the real journal is the only one that is peer-reviewed.

Read here for details: https://publons.com/blog/hijacked-journals-what-they-are-and-how-to-avoid-them/

Dear Heshu Sulaiman Rahman ,

Hijacked journals are sad examples of predatory behaviour. The scam is to copy a journal (most often a well-respected but exclusively off-line journal often with a long tradition) and present yourself as the on-line version of that journal. The fake journal is an example of a sad case of fraud and misleading practice that is unfortunately not uncommon.

Sylwan is an example that has been the victim of this practise:

https://www.researchgate.net/post/Any_one_who_has_published_in_SYLWAN_journal_Is_this_journal_FAKE_or_not

https://www.researchgate.net/post/Why_does_Google_scholar_not_find_one_of_my_recently_published_article

So hijacked journals are without a doubt predatory: why else would you pretend to be the on-line version of a journal while you are not.

Predatory journals are less clear. The term originates from a librarian called Jeffrey Beall who developed a database with possible, potential and probable journals and publishers:

https://en.wikipedia.org/wiki/Beall%27s_List

This list is archived (and somewhat unclear updated or not):

https://predatoryjournals.com/journals/

http://researchtoolsbox.blogspot.com/2019/01/bealls-list-of-predatory-journals-and.html

http://beallslist.net/

The question what predatory journals are (and how to use the Beall’s list in this discussion) is not as black and white and subject to numerous discussions and publications. See for examples:

https://www.researchgate.net/post/Bealls_list_and_scopus

https://www.researchgate.net/post/Predatory_Fake_Journals

https://www.researchgate.net/post/How_reliable_is_the_Bealls_List_of_predatory_journals

https://www.researchgate.net/post/List_of_Predatory_Journals_2019

https://www.researchgate.net/post/Is_there_a_list_of_predatory_research_journals

Article Identifying Predatory or Pseudo-Journals

Chapter How to detect and avoid predatory Journals?

Method Predatory journals and publishers: a menace to science and s...

Hope this makes the difference between the two type of journals somewhat more clear.

Best regards.