In china, there's lots of similar thing, e.g. your android phone download a app from some site, the ISP(or others in your network path) can detect this(maybe by

In china, there's lots of similar thing, e.g. your android phone download a app from some site, the ISP(or others in your network path) can detect this(maybe by url) and return a modified version(e.g. add it's own ad or maybe complete a competitor's product of the original app).