How is traffic spoofed on the web?

Question

Monitoring

How does the substitution of traffic on the Internet happen, for example, the user clicked on downloading a picture, I intercepted the download progress and uploaded another picture to him;)

Answer 1

If you can control the traffic between the user and the site, you can intercept the user's requests and spoof them accordingly. For example, a user requests site.ru/image1.jpg, and you redirect to site.ru/image2.jpg.