What is the outcome of the fraud?
You can tell the truth as publicly as you like.
The only issue here would be, in legal theory, if they dispute that your allegation is true there may be a defamation argument.
But if they are on benefits they will not be able to fund a claim anyway.
I suppose, at the highest point, there could be a harassment argument but all the police would do is tell you to take it down.
Can I clarify anything for you?
Generally speaking, people on benefits who are not worth suing do get away with murder in this country.