If IIS use old .Net Framwork it's possible to enumeration folder with the symbol ~.
Internet Information Services (IIS, formerly Internet Information Server) is an extensible web server software created by Microsoft for use with the Windows NT family. An IIS web server runs on the Microsoft .NET platform on the Windows OS.
Old .Net Framework contains an IIS Shortname vulnerability.
Update your IIS server to the latest version to eliminate this vulnerability.