The Anti-virus Times

Many people have heard that computer typography makes use of non-printable characters which are literally invisible. But this invisibility is not some kind of defect or unique feature but rather standard behaviour. Currently, UTF-8 is one of the most common text encodings, and it is being used on virtually every modern website. One of its many advantages is that it’s chock-full of invisible characters! These include, for example Zero Width Space (U+200B). Here it is: "". Can you see it? No? And yet it's right there.

https://habrahabr.ru/post/243351

A text editor or processor can render a text containing this character or take certain steps to make it visible.

Of course, the way characters are displayed depends on the specific font being used as well as on the text editor.

https://habrahabr.ru/post/311518

I remember how, many years ago, I sometimes took advantage of nonprintable characters to make my "target" max out their traffic or database storage space quota. For example, I would write "Hello! What's up?" and add thousands of invisible characters to the phrase. A short message becomes rather bulky.

…is there a way to make a text completely invisible?

We turn every byte in a string into a three-digit octal number and replace every digit with an invisible character.

https://habrahabr.ru/post/312184

The first method was used to make code look like it was written in JavaScript, while the second one changed it beyond recognition and the third rendered it completely invisible.

The code would consist of two sections: the visible section (which can be obfuscated using one of the techniques described above) and the invisible section.

As far as the visible section goes, no explanation is required. But the trick with the invisible part is this: we feed our harmful code (why else would we need to hide it?) into our obfuscation-and-invisibility engine, which turns the script from visible to invisible, i.e., a string consisting of a tab and space characters.

https://habrahabr.ru/post/112530

Ladies and gentlemen, here is an example

Let's consider this piece of code:

alert("Hello world!");

Once our obfuscation engine has processed the code (I won't go into the details because they’re not particularly interesting), it will output something like this:

Please note that the semi-colon is located inside the quotation marks, while in reality that’s not the case (you can verify this by opening it in virtually any text editor, such as Sublime ).

And here is what the decoding routine looks like:

var revealJS = function(s){return s.match(/(.{4})/g).map(function(b){return b.split('').map(function(i){return Array.apply(null,{length:10}).map(Number.call,Number).concat('abcdef'.split(''))['⁡‌‍‎‏‪‫‬‭‮'.split('').indexOf(i)]})}).map(function(c){return String.fromCharCode(0+"x"+c.join(''))}).join('')}

https://habrahabr.ru/post/243351

This is something that could happen, so it’s vital that you understand the risks involved in copying pieces of text.

https://habrahabr.ru/post/352950