HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Symantec Endpoint Protection\AV\Storages\Filesystem\RealTimeScan
on the right hand side you will find a key called OnOff
1 is file system autoprotect is on
0 means off
You need to disable tamper protection before you can make any changes here
Tamper protection can be disabled only via SEP console or via SEPM