Norton constant high disk usage

NIS is constantly writing to the C: drive and slowing down the computer.  This has been happening for some 24 hours (that I know of).

Nis.exe is constantly writing to two files: 1.4 MB/sec to CONFIG_CUR.dat and 1.1 MB/sec to CONFIG_CUR.dat.log.

-- C:\ProgramData\Norton\{0C55C096-0F1D-4F28-AAA2-85EF591126E7}\NIS_22.5.2.15\symnetdrv\CONFIG_CUR.dat

-- C:\ProgramData\Norton\{0C55C096-0F1D-4F28-AAA2-85EF591126E7}\NIS_22.5.2.15\symnetdrv\CONFIG_CUR.dat.log

Curiously, nis.exe is also sometimes writing to other files in the NIS_22.5.2.15 directory, but just a thousand or so bytes per second per file.  All of nis.exe's reported disk usage is writing to NIS_22.5.2.15, and sometimes writing to C:\$LogFile (NTFS Volume Log), 30 MB/sec.  There is no reading by nis.exe, only writing.

C: drive is reporting an average of 95% usage.

Windows 8.1.  NIS is up to date.

What is causing this?  How can I get it to stop?