No.
If you haven't done so, you should wipe the system and put a fresh OS install on it.
Is it required even when I buy it from a respected reseller business? Based on the labels it seems I've got an old i7 3770 instead of an also old i5 (yay!), but I'm yet to fire up the system as I need to grab a displayport/VGA to HDMI adapter. I bought the system for ~$130 incl. VAT.
My plan B for total safety would be to use an otherwise idle data sim card and assign an unused old phone as modem for it, that way it would be completely separated.