Hello,
Mapped drives can be a transmission pathway for malicious code and they should therefore be managed carefully. Many threats will enumerate each drive letter on the system and attempt to copy themselves to that drive, allowing for rapid spread within a corporate network. It is best to only use these drive mappings when needed, and then ensure that the content is frequently scanned for malicious threats.
The first option to protect against autorun.inf threats is to disable the functionality across the network. If this is not an option, one specific technique that is particularly effective against autorun-based threats is to create folders named ‘autorun.inf’ in all root folders of mapped server volumes. These folders should be marked as System and Hidden with the read-only bit set. Write access for these folders should be revoked for all users. Any threat that attempts to create the autorun.inf file in the root directory of a mapped drive will not be able to do so.
In SEP 12.1, If the Full Scan was created by the local user as an On Demand or Scheduled Scan, then it will treat mapped drives as local drive and scan them since both the scan and mapped network drives are created under the user context. This is still the case if the AutoProtect option to scan network drives is disabled because that is an AutoProtect feature and does not have any bearing on local manual or scheduled scans.
If a Full Scan is created by an administrator on SEPM and sent to the client in a policy, the Full Scan will not scan mapped network drives since this scan runs under the SYSTEM context.
Does a Full Scan scan Mapped Network Drives?
http://www.symantec.com/business/support/index?page=content&id=TECH96284
Symantec Endpoint Protection Recommended Best Practices for Securing an Enterprise Environment
http://www.symantec.com/docs/TECH166816
Hope that helps!!