Some of my colleagues and I have become aware of an individual (name withheld) who makes a habit of attending math conferences on false pretences in order to get travel support.
I have second-hand knowledge of a conference where they claimed an affiliation that they no longer had and they presented a paper that was blatantly plagiarized from a publication in another language. (My sources are attendees and organizers of the conference, who checked with the institution and found the source paper for the plagiarism.) A search on the web for this name (an uncommon name) shows participation and speaking at conferences in a ridiculously broad collection of mathematical areas. No one person could do original research in all those areas, so I conclude that this is serial fraud.
A few days ago, a conference for which I have some supervisory connection received a query from this individual asking for travel support. Of course, we will not be fooled, because we know better. But how many other conferences will be fooled? Is there a mechanism for stopping this sort of thing?
(One thing that I think will not work: Contacting their current institution, because it's likely that they are currently unaffiliated.)