My MacBook Pro was hacked. A chess board appeared and when I clicked it code scrolled all over the screen and then my desktop disappeared. It all came back but now it shows a guest user and my screen looks completely different.

Question

Files on my computer were added. In the files were pics of my hard drive and flags. Text editor had a lot of code. Is there anyway to convert the code? Trying to see if my crazy ex did this. And did someone have to have access to my computer to do this?

Answer 1

Disconnect from the network.
Back up all data to at least two different storage devices, if you haven't already done so. The backups can be made with Time Machine or with a mirroring tool such as Carbon Copy Cloner. Preferably both.
Reconnect to the network.
Boot into Recovery (command-R at startup), launch Disk Utility, and erase the startup volume with the default options.This operation will destroy all data on the volume, so you had be better be sure of your backups. Quit Disk Utility and install OS X. When you reboot, you'll be prompted to go through the initial setup process. That’s when you transfer the data from one of your backups. For details of how this works, see here:
Using Setup Assistant
Transfer only "Users" and "Settings" – not "Applications" or "Other files." Don't transfer the Guest account, if it was enabled on the old system.
Reinstall your third-party software from fresh downloads or original media.
Change all Internet passwords.
Note: You need an always-on Ethernet or Wi-Fi connection to the Internet to use Recovery. It won’t work with USB or PPPoE modems, or with proxy servers, or with networks that require a certificate for authentication.