How to remove the trogan

First try

How to install adware

Stop pop-up ads and adware in Safari

Remove unwanted adware that displays pop-up ads and graphics on your Mac

Adware Removal Guide : Identification

Next:

Malwarebytes for Mac (was Adwaremedic)

Removing/disabling extension and some other actions also apple to browsers besides Safari

First, never use any kind of "anti-virus" or "anti-malware" software on a Mac. That's how you create problems, not how you solve them.

From the menu bar, select

 ▹ System Preferences... ▹ Network ▹ Advanced... ▹ DNS

Under DNS Servers you should have one or more numerical addresses, such as “192.168.1.1” or “10.0.0.1”. What are those addresses?

Please back up all data.

Unlock the Network preference pane, if necessary, by clicking the lock icon in the lower left corner and entering your password. Cllck Advanced, open the DNS tab, and change the server addresses to the following:

8.8.8.8

8.8.4.4

That's Google DNS. Click OK, then Apply.

In Safari, select

Safari ▹ Preferences... ▹ Privacy ▹ Remove All Website Data

and confirm. If you’re using another browser, empty the cache. Test. Any difference?

Notes:

1. If you lose Internet access after making the above change to your network settings, delete the Google servers in the Network preference pane, then select the TCP/IP tab and click Renew DHCP Lease. That should restore the original DNS settings; otherwise restore them yourself. Remember that you must click Apply in order for any changes to take effect.

2. I don't use Google DNS myself, though I have tested it, and I'm not recommending it or any other DNS provider; the server addresses are offered merely for testing purposes. There may be privacy and technical issues involved in using that service, which you should investigate personally before you decide whether to keep the settings. Other public DNS services exist.

Your router has been hacked to direct DNS queries to a malicious server.

Follow the manufacturer's instructions to reset the router to the default state. Usually that involves inserting the end of a straightened paper clip or a similar tool into a pinhole somewhere in the back of the device, and pressing a switch inside for about 15 seconds. The pinhole may be marked "RESET."

Repeat the initial setup process. Make sure the router does not allow remote setup from the Internet (WAN port), if it has that feature—most do. The DNS servers should be set automatically by your ISP. If you still have trouble with those servers selected, contact your ISP.

Check the router manufacturer's website for a firmware update.

If you have a wireless network, it must be secured with WPA 2 encryption. The passwords for the network and the router must each be a string of at least 10 random upper- and lower-case letters and digits, and they should be different. Any password that you can remember is weak.