using System;
using System.IO;
using System.Security.AccessControl;

namespace secur
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("path > ");
            var path = Console.ReadLine();

            const string usr = @"domain\user";
            SetPermissions(path, usr);
        }

        public static void SetPermissions(string folderPath, string domainAndUsername)
        {
            var ds = Directory.GetAccessControl(folderPath);
            var fsac = new FileSystemAccessRule(domainAndUsername,
                                                FileSystemRights.FullControl,
                                                InheritanceFlags.ObjectInherit,
                                                PropagationFlags.InheritOnly,
                                                AccessControlType.Deny);

            ds.AddAccessRule(fsac);
            Directory.SetAccessControl(folderPath, ds);
        }
    }
}