It's not a "hacking attack", it's an element on a website:
<iframe src=http://bylock.net width=1 height=1>
or
<img src=“http://bylock.net” width=1 height=1>
This code, if it was a part of a page you browse, would cause your browser to load the linked site, almost exactly like clicking on this link:
http://bylock.net. This iframe was present in various websites and apps.
The nefarious component of the attack is that the Turkish government surveils all Internet traffic within its borders and thought that the website may have helped some of its opponents commit what it believes to be treason. Its surveillance data tells it all the sites your phone looks up, and it accused people whose phones looked up that domain as being guilty of treason.