I think I might have a virus on my mac, what should I do?

Question

So I downloaded this thing that told me if I downloaded it, I could watch a TV show I was looking for
on it (ridiculous, I know) but ever since, I get these boxes that'll pop up on every site I go on (except for maybe facebook) and they display adds, it also will use certain words on a site and make them into links to send you to other sites or whatever that are irrelevant. I've attached a picture of what it looks like, it happens on netflix especially, every single time. I used a virus finder and tried to delete everything it found that was suspicious but its still going on, should I just wipe my whole computer back to factory setting?

Answer 1

There is no need to download anything to solve this problem. You installed the "Flashmall" trojan. Take the steps below to disable it.
Malware is always changing to get around the defenses against it. This procedure works as of now, as far as I know. It may not work in the future. Anyone finding this comment a few days or more after it was posted should look for a more recent discussion, or start a new one.
Back up all data before continuing.
1. Triple-click the line below on this page to select it, then copy the text to the Clipboard by pressing the key combination  command-C:
~/Library/LaunchAgents
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. A folder named "LaunchAgents" will open.
2. Inside the folder you just opened, there may be files with a name beginning in any of the following ways:
           com.crossrider
           com.extensions
           com.flashmall
           com.webhelper
           com.webtools
           flashmall
           UpdateDownloader
           WebSocketServerApp
Some of these files may be absent. Move any that you have to the Trash and close the Finder window. Log out or restart the computer. The trojan will now be inactive, but there are a few more components of it that should be cleaned up.
3. Do as in Step 1 with this line:
~/Library/Application Support
A folder named "Application Support" will open. Inside it there may be a subfolder with this name:
            webHelperApp
If so, move that subfolder—not the "Application Support" folder—to the Trash.
4. Open this folder in the same way as above:
~/Library/ScriptingAdditions
and remove an item named
            BrowserHelper.osax
if present.
5. Open this folder:
~/Library
Look for subfolders with either of these names:
            flashmall
            WebTools
and move them to the Trash, if present.
6. Open the Applications folder. If it contains an item named "Flashmall" or "WebTools", move that to the Trash.
Empty the Trash.