Mac's don't need defragging as OS X automatically writes 2Gb or below sized files to one contiguous space on the drive. There are certain cases where's it's needed to free up a large spaces on the drive, but not something everyone has to do.
Far as other Mac maintainence, there really isn't any except to backup one's files regularly. Keeping Software Updated and run a web browser check to make sure the plug-ins are current.
Mar 08, 2017 CCleaner is one free and top Mac cleaner to delete cookies, search history, temporary files and junk files from Mac. The specific functions are below: 1. Find and remove useless/junk files with the click of a button so your Mac can run faster. Jan 14, 2018 DU Speed booster & Cleaner Download This app is one of the most popular free cache cleaner apps on Play Store. It’s a speed booster, ram booster, game booster, junk file cleaner, trash cleaner, memory booster, battery optimizer and app manager — all in one!
For Safari and Flash, this check is more accurate
Most of those cleaning programs are junk, especially MacKeeper.
![Top free mac cleaner apps online free Top free mac cleaner apps online free](https://www.softwarehow.com/wp-content/uploads/Macintosh-HD-Storage-macOS-High-Sierra.jpg)
If your friend got onto your computer and visited a bunch of adult sites, then I would recommend something like OnyX, doing ALL the cleaning and maintenance aspects and rebooting, perhaps followed by a Disk Utility Erase free space.
CCleaner beta is out for OS X, used on PC's and combines cleaning and scrubbing of the drive if setup correctly.
If your interested in performance, read my post here