SerDef.dat
An encrypted file that stores communication settings by location. Each time the user changes locations, the SerDef.dat file is read and the appropriate communication settings for the new location are applied to the client.
sylink.xml
Stores the global communication settings. This file is for internal use only and should not be edited. It contains settings from the Symantec Endpoint Protection Manager. If you edit this file, most settings will be overwritten by the settings from the management server the next time the client connects to the management server.
SerState.dat
An encrypted file that stores information about the user interface, such as the client's screen size, whether the client's console for Network Threat Protection appears, and whether Windows services appear. When the client starts, it reads this file and returns to the same user interface state as before it was stopped.