I believe that money is a tool, and one has to be careful who they give tools to. You would not hand a delicate instrument to an unskilled person. Likewise handing money to someone that you don’t know means that you are giving them the means to an end that you are unsure of. Even giving a small amount empowers and emboldens. If Hashem entrusted you with money, He obviously expects you to treat it very carefully and to investigate where your money is being used. With so many Jews unable to pay for basics these days, there are many legitimate ways to put your maaser money to use.
One thing we do is pay tuition for a child to attend a BY school. Her mother pays a small amount and was told her child qualified for a scholarship. This mother is a divorced mother not receiving money from her ex. Every time my own children take a small job, they put their maaser into this tzedaka. All their small change and ours adds up every month! We all feel very happy to be giving to this cause. When others come asking for tzedaka, we honestly tell them that our money goes to one specific cause and because of that we are unable to help them at this time. Most tzedaka collectors respect that and no one has ever made me feel bad. I think that when others recognize that you are genuine, and that you would like to help, but that you are committed elsewhere, it gives koach.