In Windows 8 it is 'Windows Defender' security tool that is supported. In other words, there is no 'Microsoft Security Essential' support for Windows 8 or Windows 8.1.
An Update to the Thread Titled: "[Download:] MS Security Essentials v4-4-304-0 (System Center Endpoint Prot.) for W8-x" Possibly that is why.
I search Microsoft System Center 2012 R2 Configuration Manager and System Center 2012 R2 Endpoint Protection But is just for TechNet
System Center Endpoint Protection is present on MU_SYSTEM_CENTER_2012_R2_CONFIGURATION_MANAGER_X86_AND_X64_DVD_2926949.iso in \SMSSETUP\CLIENT\scepinstall.exe. But it is an old version v4-3-220-0... ... for new one use Tito's link...