MsMpEng.exe just ran alongside another process named “0day.exe” (or something similar)

OS: Win 7 x64 Ultimate

Just after waking up my computer from sleep and hearing the HDD being accessed repeatedly a few hours later (disk access sounds, 2 seconds of silence, repeat for about 10 seconds), I was curious to see what processes were running, even though I knew that it was likely Windows Update, svchost, or some combination of usually innocuous programs running for online updates or diagnostic purposes. As such, seeing MsMpEng.exe (Microsoft Windows Defender Antispyware) in the Task Manager with 6% CPU usage wasn't very surprising, but then I very briefly saw something closely named to "0day.exe" also running at the same time. I say "closely" because it was so briefly in the list that I couldn't see the precise name, but did catch that it seemed to contain all said characters in its name, which is suspicious.

I've never seen this process before and I regularly have checked and monitored the Task Manager over many years of using Win 7 in a very closed environment.

Has anyone seen a similarly named program running while Windows Defender is running or otherwise?

Possible ideas: ** Microsoft recently updated its security suite to scan for zero-day related stuff and "0day.exe" is a legitimate program scanning for anomalous behaviour. ** My PC is infected with malware and I should probably just throw the machine out because it will never be patched due to its age. ** Keep the PC and leave it disconnected from the internet and all new hardware. ** Try not to cry and then cry.