Bing hijacking my safari smart search field

Question

Hi all,
after updating to Yosemite recently I have noticed that whenever I type a search into the safari smart search field, the results are redirected through the bing search engine.
I have tried changing it to Google, through the safari preferences and Duckduckgo too but its all to no avail. Everytime, the search returns bing suggestions. I hate bing, but I hate not having control over the search even more.

Answer 1

I doubt that the uninstaller completely removes the malware. Like "InstallMac" itself, it's distributed by a criminal.
You installed the "InstallMac" trojan. I suggest the procedure below to disable it. This procedure may leave a few small files behind, but it will permanently deactivate the trojan (as long as you never reinstall it.)
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 one called "Omnibar," and any that have the word "Conduit," "Spigot," or "InstallMac" in the description. If in doubt, uninstall all extensions. Do the equivalent for the Firefox and Chrome browsers, if you use either of those.
Step 2
In the Applications folder, there may be items named "Installer," "InstallMac," "Reset Search," or "Uninstall IM Completer." Drag each such item to the Trash.
Step 3
Triple-click anywhere in the line below on this page to select it:
~/Library/LaunchAgents/com.genieo.completer.download.plist
Right-click or control-click the line and select
          Services ▹ Reveal in Finder (or just Reveal)
from the contextual menu.
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.
A folder should open with a file named "com.genieo.completer.download.plist" selected. There may be other files in the folder with a name beginning in "com.genieo." Move them all to the Trash.
Move this folder, if it exists, to the Trash in the same way:
~/Library/Application Support/com.genieoinnovation.Installer
Log out or restart the computer and empty the Trash.
Make sure you don't repeat the mistake that led you to install this trojan. Chances are you got it from an Internet cesspit such as "Softonic" or "CNET Download." Never visit either of those sites again. You might also have downloaded it from an ad in a page on some other site. The ad has a large green button labeled "Download" or "Download Now" in white letters. The button is designed to confuse people who intend to download something else on the same page. If you ever download a file that isn't obviously what you expected, delete it immediately.
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 this attack 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.