Microsoft IIS tilde directory enumeration, security issue. (4350443)

This can show up in a security scan of web applications, i.e.  Acunetix.

This is a  config problem in IIS.

There is a way to disable Windows 8.3 short name creation.You can create a registry key named NtfsDisable8dot3NameCreation in HKLMSYSTEMCurrentControlSetControlFileSystem and set it to 1.  That should disable short names creation. Refer to this Microsoft TechNet article to read more about the solution.
(source: http://www.acunetix.com/blog/web-security-zone/windows-short-8-3-filenames-web-security-problem/)