I am not aware of a way to lock down access to those directories. Have you tried disabling HTTP and enabling HTTPS? Then run the same scan and see if the outcome is the same.  You might try a firmware update. There are some security improvements in the latest firmware. [URL] If it is a must to disable the web interface,the switch can be fully managed through the CLI. 
Hello, After a recent vulnerability scan with BeyondTrust Retina, our PC 5524 showed hits such as:  Besides disabling the web interface, is there any way to lock down access to those directories? Thank you.
Options to lock down PowerConnect 5524 after vulnerability scan