IMac – Mysteriously, a rectangle has appeared in the middle of the screen. How to get rid of it

hackingimacmacosSecurity

I have a iMac (27-inch, Late 2009) running OS X Yosemite v 10.10.2. Mysteriously, a rectangle has appeared in the middle of the screen.

Proportionately, it looks like a golden section.
It floats on top of everything else.

enter image description here

Close up:

enter image description here

Almost like a ghost of something, but I don't remember opening anything that size.

Any ideas about this?

Could someone/something have hacked my machine?

How do I get rid of it?

Best Answer

Steps to evaluate where it comes from.

  1. Switch User to see if it is user specific

  2. Restore Disk permissions.

  3. Start in Safe mode to eliminate 3d party applications

  4. It looks like it is a left over from some app that did not close properly, next time if it happens remember what app you just closed.

If problem persists, use Apple Hardware Test.

Related Question