IECompat entries relate to the Internet Explorer compatibility list maintained by Microsoft. See Internet Explorer Compatibility.
iecompat entries in NetAnalysis v1.5x
Internet Explorer Compatibility Cache in AppData\Roaming
C:\Users\{user}\AppData\Roaming\Microsoft\Windows\IECompatCache\index.dat
C:\Users\{user}\AppData\Roaming\Microsoft\Windows\IECompatCache\Low\index.dat