For a friend, I’m setting up a Win 8.1 Pro 64 bit laptop purchased from Dell Refurbished. I’ve installed Opera, Firefox, Gimp and about 100 games from Big Fish. All the preceding software is up to date, as is Windows 8.1 (through October with what used to be called Group A).
When I do either a quick or full scan with Windows Defender I get a yellow triangle/exclamation point with the statement that preliminary results indicate the presence of malware or other potentially unwanted software and that I can review the affected files at the end of the scan. But, at the end of the scan, the triangle/exclamation point and message all disappear and at the top of the Defender Dialog box I get a green check mark, a statement of the number of files scanned and that my computer is being protected. The History box is empty. Well OK, its probably nothing, but…
… in an effort to determine what files weren’t “liked”, I did a bunch of custom scans to try and narrow down where the file(s) is(are). No matter what custom scan I try I never get the triangle/exclamation point/warning message, and when the scan is done I get the green check mark, a statement of the number of files scanned, a statement that my computer is being protected, AND a statement that no infected files were found. This last statement never showed up after a quick or full scan (although it always shows up on my own 8.1 computer when I do a quick or full scan and nothing is found). The other interesting thing is that after I do a custom scan on the C: drive, the reported number of files scanned is smaller (by about 25000) than the number reported for a full scan.
So, my questions are, is the occurrence of the triangle/exclamation point/warning statement of any significance? If so, how do I find the suspected file? Also, shouldn’t the number of files scanned be the same for a custom scan of C: as for a full scan?
I’ve run the Microsoft Safety Scanner (downloaded from this link https://docs.microsoft.com/en-us/windows/security/threat-protection/intelligence/safety-scanner-download) and everything comes up completely clean.
I’ve also rum Malwarebytes Free, which also came up totally clean, but interestingly, said it only scanned about 280,000 files (as opposed to more than 600,000 files for a full scan or custom C: scan with Defender).
I’d appreciate any insight into what’s going on, particularly on whether this is worth pursuing and/or how likely it is that something is infected. This laptop is a gift, and while I suspect it will not be heavily used for internet surfing, I’d really like to get this right.
Thanks.