As far as I know Catholics ought to give due regard to St. Matthew's Gospel, Chaper 25, Verses 31 - 46, and the Corporal Works of Mercy, also not to forget the First Epistle of St. Peter, Chapter 4, Verse 8:
But before all things have a constant mutual charity among yourselves: for charity covereth a multitude of sins.I'm thinking one ought not to just stop giving, but prudence and due diligence are in order.
Charity Navigator is a source many use to evaluate regional, national, and international charities. They provide evaluations of charities based on several parameters, and show what percentage of an organization's income is spend on programs, administration, fundraising expenses, etc.
Focusing one's giving on local organizations is another option, and one should have the opportunity to see their work, ask direct questions in person, etc. I've never heard a problematic story about a St. Vincent DePaul Society local Conference, or example. They are connected to the diocesan Church and I appreciate that may be problematic for some traditionalists. So, a similiar type of apostolate could be organized at one's chapel.
There are also many ways to give besides just cash. Many people donate produce from their gardens to local food banks. Groups like Meals on Wheels always need volunteers to prepare and deliver meals to shut ins. Food banks need volunteer workers and some, especially some St. Vincent DePaul groups I'm aware of, need people to repair donated furniture and appliances and to mend donated clothing before distribution.
Many churches have some type of care ministry in which volunteers give the elderly who don't drive rides to appointments (and to church), prepare and deliver meals to families where the mother just had a baby, or to someone recuperating after an illnes, surgery, or cancer treatment. This may also include help with housekeeping or baby sitting. Many churches have programs where food is taken to a family after a death, and a hot meal is provided in the parish hall the day of the funeral.
There are lots of ways to practice charity without having to write checks or to worry about being taken advantage of, with a little bit of effort and research.