Cory makes some good suggestions. Earlier last week, I got "hit" by a Bit Coin-related virus on my mid 2013 13" MacBook Air (never used Bit Coin "services" at all), and I downloaded and used the freeware virus removal program by Sophos to get rid of it. (ClamXav did not detect it). But, the machine still ran somewhat slow, especially using the latest version (at that time) of Google's Chrome browser (I do not have this issue on my MacMini). I subsequently re-booted the machine from my most recent SuperDuper! backup, used Disk Utility there to Erase/Format/Partition (only 1 partition) the internal 256 gig SSD on the machine, did a restore from the backup, and re-booted the Air. I also applied some software updates (including a newer version of Chrome), and "re-built" both TechTool Pro's eDrive and the Recovery Partition. The machine did seem to respond better. But, Chrome is now slower than Safari on the machine. There are some sites that I go to where it is fast, but others where it is slow. That's especially the case where I launch Chrome, and it goes to my home site (this one, ie, Mac Help) It is somewhat slow, especially compared to Safari, and to Chrome on my MacMini.
I'm almost tempted to completely wipe the SSD clean, install Yosemite "piece by piece" (that is, install 10.10.0, and then upgrade to 10.10.3), and then install all my applications. But, that sure would be a headache, especially with re-setting up my Internet services with Comcast. For now, the machine is working good enough.
I even contemplated wiping that SSD clean again (doing it the longest way via Disk Utility), formatting and partitioning it (one partition only), and then doing a SuperDuper! restore from the latest
MacMini backup (also subsequently installing any further updates, and re-building both TechTool Pro's eDrive and the Recovery Partition). Is that somewhat "impossible", in that there are/could be some specific files/settings, etc. that are unique to the MacBook Air? In fact, would that be more for the case of Yosemite (OS 10.10.3), with all its' related libraries, system files, settings, etc.?
Regarding Cory's list, I have more than half of
each SSD in
each machine free, I rarely run more than one application simultaneously, and I do not have MacKeeper on either machine. The only anti-virus software I have is ClamXav.
The perplexing thing is that I am not having
any of these issues with my late 2012 MacMini. I use the same disk maintenance/repairs/backup programs (Onyx, TechTool Pro, and SuperDuper!) on both machines, and keep both machines "lean and clean", especially between my weekly backups. Google's Chrome works fine, and is definitely fast (the MacBook Air was the same prior to the Bit Coin-related virus). If anyone knows any more detective work I could do on the Air, I would appreciate any ides, suggestions, etc.
As for the pop-ups, etc., the link Cory provided is definitely worthwhile. And, especially what he stated regarding MacKeeper. If it is on your machine (look inside your Applications folder), you
DEFINITELY need to get rid of it. You can also download, install, and run the excellent freeware program AdwareMedic. You can get it from here:
http://www.macupdate.com/app/mac/52105/adwaremedic
I use it every so often. Even after the onslaught of the Bit Coin virus, I used it, and it found no issues (have not been having problems with pop-ups).