Since 15.Mar.2017 I've been getting a yellow triangle warning during every Microsoft Security Essentials scan on my Windows 7 laptop. It always shows up whilst the scan is checking =svchost= and remains on screen for the rest of the scan - Quick or Full. Yet, when the scan completes, I get a green tick on the Home tab and nothing in any of the subdivisions of the History tab.
New false positive, or new malware that is somehow suppressing reports of its existence?
[Added 12.May.2017 : Problem disappeared at next monthly update of Windows 7 and has not been seen again since then.]