I compressed some pictures it a zip file. Next, I opened this zipped file with Notepad++, changed it a bit and saved it. As expected, in this condition the zipped file doesn't open up.
When I undo the changes I made to the zip file, it opens up and the pictures are still there!
My question is, is this a good method to secure my personal files? Most importantly is it possible that the changes of the code could be undone by a software or other ways?