using System;

using System.Collections.Generic;

using System.Text.RegularExpressions;

using System.Threading.Tasks;

​

public class Program

{

    public static void Main()

    {

        var cc = "4444-0000-1111-2222";

        var reg = new Regex(@"(\d{4})(?: |-)?(\d{2})(?:\d{2})(?: |-)?(?:\d{4})(?: |-)?(\d{4})");

        cc = reg.Replace(cc, new MatchEvaluator((m) => new String('*', m.Length)));

        Console.WriteLine(cc);

    }

}