I've been arguing about this for the last three days. Mostly around the reason that "complexity" is not strictly the same thing as "sophistication" when it comes to software. Noobs will conflate the two, but experienced programmers will agree that -- just to illustrate my point -- some code which solves a complex problem in a very clever way while also being very clean and easy to maintain will be considered strictly more sophisticated than some other code solving a similar problem which simply has a higher degree of complexity than the former. There
is a subtle difference when it comes to software, and this subtlety needs to be considered in this question. Now, I think Stuxnet is a fantastic suggestion to this question, for a number of reasons:
1) The legal, ethical, technical challenges of creating the software.
2) The ability of the software to remain hidden in (sophisticated) environments rich with (sophisticated) organizations looking for exactly this kind of thing.
3) The stealth of the entire research, design, development, and deployment phases of the project.
4) The highly specialized nature of the target.
5) The scale of the entities involved.
6) All of this sophistication and we can't even see the source code (decompilation doesn't count).
This is frankly some impressively sophisticated software. Also, incidentally, the Quora poster's company looks like a fun place to work (with good programmers on the team). Some of his other answers are thoughtful and interesting to read, too, if you get the chance.
1) The legal, ethical, technical challenges of creating the software.
2) The ability of the software to remain hidden in (sophisticated) environments rich with (sophisticated) organizations looking for exactly this kind of thing.
3) The stealth of the entire research, design, development, and deployment phases of the project.
4) The highly specialized nature of the target.
5) The scale of the entities involved.
6) All of this sophistication and we can't even see the source code (decompilation doesn't count).
This is frankly some impressively sophisticated software. Also, incidentally, the Quora poster's company looks like a fun place to work (with good programmers on the team). Some of his other answers are thoughtful and interesting to read, too, if you get the chance.