These kinds of vague rumours ("they have evidence" is weasel words) are used to legitimize the development of invasive programs (and software) that profile people; see for example https://en.wikipedia.org/wiki/Dutch_childcare_benefits_scand... that affected tens of thousands of people (causing children to be removed from their parents, divorces, suicides, etc), mostly justified because of a small group of people defrauding the benefits scheme. The total cost of setting this right is in the billions and increasing, many times more than whatever they saved on fraud.