Is it better to reinstall Mac OS to clear up malware issues or erase then restore to factory settings?

Can you explain how you know there is Malware on the device?  Just curious, as while not impossible, it is not common either. Might just be a corrupted app or preferences file causing the problem.

The problem with a full erase and restore is reinstalling all the applications, which means finding all the keys and install media, which takes a lot of time. You do not want to restore from a backup unless you are sure the backup was malware free.

The positive side is that it is the best way to be sure your malware is gone, and you get a clean system, so things will run a bit faster as well.

You could also install a malware detection product (I like Webroot), and have it scan and remove the malware. I have been very successful with this as well.

@Scott,
Thank you.
>> I would also make some sort of full backup just in case they later find something missing they needed that wasn't saved.
Is having iCloud turned on sufficient enough or do I need to backup with Time Machine?  

@Owen,
Thank you.
>> Can you explain how you know there is Malware on the device?  Just curious, as while not impossible, it is not common either. Might just be a corrupted app or preferences file causing the problem.
I do not have any other information at this time.  They were told they have malware by an Apple tech I think.

>> You could also install a malware detection product (I like Webroot), and have it scan and remove the malware. I have been very successful with this as well.
I appreciate the recommendation!

I'll be tackling this task in a few hours from now so I'll update later after I've done an erase and restore.

Is having iCloud turned on sufficient enough or do I need to backup with Time Machine?  

Would depend on what they set to backup to the cloud.

I would recommend doing a full Time machine backup before changing anything as that gives you a full recovery if anything should go astray. And somehow, as simple as these things are, they always seem to go astray.   :-)

Happy to answer any other questions.

Better do a Full Disclosure: I am a Webroot Community Advisor on their forum and also a member of  Webroot Luminaries, so I may have a bias here. I do not get paid nor do I get anything for recommending them. I just joined there because I felt their product was that good.  Just wanted to make sure I disclosed this.

I have also used the free Avira product.

I think you're OK.  I use Webroot already on my machine haha.  Thanks for the additional information!

Thanks. I just like to be upfront about things like that, and forgot to add it to my post.

It depends on the malware.  What kind is it? If it's kernel level, then, yes, wipe the system and reinstall.  If it's some BHO, then run something like Malware Bytes and have it clean it up.  Reinstalling without erasing the disk will not remove a BHO, but it will restore trojaned kernel files.  You can also remove the Preferences and Library files for the particular browser.  For Macs, it's usually a BHO that "infects" the system.  Windows viruses still do not affect the Mac.

P.S. Macs were never more secure.  They were just ignored.  They can be more easily taken over than most people think.

I erased the disk and reinstalled the new mac os and it went as well as I could hope for.  I learned something new today so that was cool. =)

Excellent