Browser Virus Malware Adware etc. HELP!

Question

I have been trying for 3 days to kick this absurd problem off of my Macbook Pro.  It feels like I have a virus/malware/adware situation that is making me feel like I'm back on a PC (UGHHHHH).
BEFORE THE PROBLEM:
I kept getting "scratchdisk" or "startup disk" is full notices so I could not download the new OS
I started searching the web for solutions
I started removing all unneeded files
I used Clean My Mac to remove unwanted/unneeded files
I downloaded OS X 10.9.5
THE PROBLEM:
The following things occur when I attempt to use any of the 3 browsers: Google Chrome, Safari, Firefox:
pop up windows appear ALL over the place
Pop up windows block my ability to use the intended web page
tabs automatically open for Wix, Mackeeper, Credit Check websites etc.  (It's infuriating!)
Sites I am attempting to use fail to respond
ACTIONS TAKEN:
run Clean My Mac (nada)
delete all cookies (nada)
trash or uninstall any/all unknown apps/programs
uninstall Google Chrome
uninstall Firefox
reset Safari
some terminal exercise from an Apple forum (did...nada)
RESOLVE:
NOTHING seems to be working...I'm about to launch my computer out the window... HELP!?

Answer 1

There is no need to download anything to solve this problem.
A.
You may have installed the "VSearch" trojan. Remove it as follows.
Malware is always changing to get around the defenses against it. These instructions are valid as of now, as far as I know. They won't necessarily be valid in the future. Anyone finding this comment a few days or more after it was posted should look for more recent discussions or start a new one.
Back up all data before proceeding.
Step 1
From the Safari menu bar, select
          Safari ▹ Preferences... ▹ Extensions
Uninstall any extensions you don't know you need, including any that have the word "Spigot," "Trovi," or "Conduit" in the description. If in doubt, uninstall all extensions. Do the equivalent for the Firefox and Chrome browsers, if you use either of those.
Reset the home page and default search engine in all the browsers, if it was changed.
Step 2
Triple-click anywhere in the line below on this page to select it:
/Library/LaunchAgents/com.vsearch.agent.plist
Right-click or control-click the line and select
          Services ▹ Reveal in Finder (or just Reveal)
from the contextual menu.* A folder should open with an item named "com.vsearch.agent.plist" selected. Drag the selected item to the Trash. You may be prompted for your administrator login password.
Repeat with each of these lines:
/Library/LaunchDaemons/com.vsearch.daemon.plist
/Library/LaunchDaemons/com.vsearch.helper.plist
/Library/LaunchDaemons/Jack.plist
Restart the computer and empty the Trash. Then delete the following items in the same way:
/Library/Application Support/VSearch
/Library/PrivilegedHelperTools/Jack
/System/Library/Frameworks/VSearch.framework
~/Library/Internet Plug-Ins/ConduitNPAPIPlugin.plugin
Some of these items may be absent, in which case you'll get a message that the file can't be found. Skip that item and go on to the next one.
The problem may have started when you downloaded and ran an application called "MPlayerX." That's the name of a legitimate free movie player, but the name is also used fraudulently to distribute VSearch. If there is an item with that name in the Applications folder, delete it, and if you wish, replace it with the genuine article from mplayerx.org.
This trojan is often found on illegal websites that traffic in pirated content such as movies. If you, or anyone else who uses the computer, visit such sites and follow prompts to install software, you can expect more of the same, and worse, to follow.
You may be wondering why you didn't get a warning from Gatekeeper about installing software from an unknown developer, as you should have. The reason is that the Internet criminal behind VSearch has a codesigning certificate issued by Apple, which causes Gatekeeper to give the installer a pass. Apple could revoke the certificate, but as of this writing has not done so, even though it's aware of the problem. This failure of oversight has compromised both Gatekeeper and the Developer ID program. You can't rely on Gatekeeper alone to protect you from harmful software.
*If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination  command-C. In the Finder, select
          Go ▹ Go to Folder...
from the menu bar and paste into the box that opens by pressing command-V. You won't see what you pasted because a line break is included. Press return.
B.
Remove "MacKeeper" as follows. First, back up all data.
"MacKeeper" is a scam with only one useful feature: it deletes itself.
Note: These instructions apply to the version of the product that I downloaded and tested in early 2012. I can't be sure that they apply to other versions.
If you have incompletely removed MacKeeper—for example, by dragging the application to the Trash and immediately emptying—then you'll have to reinstall it and start over.
IMPORTANT: "MacKeeper" has what the developer calls an “encryption” feature. In my tests, I didn't try to verify what this feature really does. If you used it to “encrypt” any of your files, “decrypt” them before you uninstall, or (preferably) restore the files from backups made before they were “encrypted.” As the developer is not trustworthy, you should assume that the "decrypted" files are corrupt unless proven otherwise.
In the Finder, select
          Go ▹ Applications
from the menu bar, or press the key combination shift-command-A. The "MacKeeper" application is in the folder that opens. Quit it if it's running, then drag it to the Trash. You'll be prompted for your login password. Click the Uninstall MacKeeper button in the dialog that appears. All the other functional components of the software will be deleted. Restart the computer and empty the Trash.
☞ Quit MacKeeper before dragging it to the Trash.
☞ Let MacKeeper delete its other components before you empty the Trash.
☞ Don't try to drag the MacKeeper Dock icon to the Trash.