You installed the "Genieo" search-hijacking rootkit. There is an uninstaller, but as the developer is dishonest, you can't use it. I suggest the tedious procedure below to disable Genieo.
Back up all data. You must know how to restore from a backup even if the system becomes unbootable. If you don't know how to do that, or if you don't have any backups, stop here and ask for guidance.
Triple-click anywhere in the line below on this page to select it:
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, paste into the box that opens (command-V). You won't see what you pasted because a line break is included. Press return.
A folder may open with a file selected, or the file may not exist, in which case you'll get a message that it can't be found. If it does exist, it's a configuration file created or replaced by the Genieo installer. Any software installer that does this should be considered ipso facto malware. Move the file to the Trash. You'll be prompted for your administrator password. Then restart, empty the Trash, and continue as below.
IMPORTANT: If the launchd.conf file exists, you must move it to the Trash and restart before continuing. Otherwise the system may become unbootable. In that case, restore from your backup and start over. That's how badly Genieo has sabotaged your system. If you're not completely sure you can complete this step, stop here and ask for guidance.
Some variants of Genieo don't include the launchd.conf file. The absence of that file doesn't mean that Genieo is not installed.
Once you have trashed the launchd.conf file and restarted, or verified that the file doesn't exist, quit the Genieo application, if it's running. Force quit if necessary.
Move each of these items to the Trash in the same way as above:
There's no need to restart after each one. Again, 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.
Restart and empty the Trash. Don't try to empty the Trash until you have restarted.
Your web browser(s) should now function normally, and you should be able to reset the home page and search engine. If not, stop here and post your results.
From the Safari menu bar, select
Safari ▹ Preferences... ▹ Extensions
Uninstall any extensions you don't know you need, including ones called "Genieo" or "Omnibar," and any that have the word "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.
This procedure may leave a few files behind, but it should deactivate Genieo. Make sure you don't repeat the mistake that led you to install it. Chances are you got it from one of the Internet's open sewers 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.
Finally, be forewarned that when Genieo is mentioned on this site, the developer sometimes shows up under the name "Genieo support." If that happens, don't believe anything he says, but feel free to tell him what you think of his scam.