1. A method comprising: detecting fraudulent clicks performed towards an on-screen advertisement; wherein the detecting comprises: (a) presenting to a user of an electronic device, a screen comprising content and said on-screen advertisement; (b) injecting a temporary input/output interference that causes an on-screen pointer, that is on route to click within said on-screen advertisement, to exhibit irregular behavior from its regular route; wherein the injecting comprises: injecting a temporary input/output interference that replaces the on-screen pointer with both: (I) a real on-screen pointer that is visible to human users and is detectable by computerized scripts, and (II) a fake on-screen pointer that is invisible to human users and is detectable by computerized scripts; wherein said temporary input/output interference causes human users to click within said on-screen advertisement, and causes computerized scripts to click outside of said on-screen advertisement; (c) tracking user interactions with an input unit in response to said temporary input/output interference; (d) determining that said user did not perform sufficient manual correction operations that fix said temporary input/output interference; (e) based on step (d), determining that a click performed within said on-screen advertisement, was performed by a click-fraud mechanism.