So I've got an iMac that's about 5-6 years old. Runs great, still does what I need; no problems at all. Today, for the first time ever, when I turned it on from completely powered down, during the power up I got this pop-up on the screen called TuneUpMyMac. Have never seen this before. Looks like it was scanning about four different areas. It supposedly found 1925 issues and has a button that says "Clean Now". Is this junk that has somehow made it onto my machine? What can I or should I do about it? Thanks for any help.