In the early days of the internet (and still on poorly configured servers today), webmasters sometimes forget to disable "directory browsing." When you visit a normal website, you see a pretty HTML page. When you hit an "index of" page, you see a raw list of files—usually .mp4, .avi, or .mkv files.
The "!FULL!" modifier in the search query implies the user wants the complete season (episodes 1 through 24, plus The Final Break movie). Users search for this string hoping to find an unlocked server folder where they can right-click and download every episode in one go.
Those raw .exe files disguised as .mp4 are everywhere. Hackers know that Prison Break fans are desperate. They upload files named S04E07.mp4.exe or force you to download a "codec" to watch the video. That codec is usually ransomware or a keylogger.
Before you start clicking on those raw IP addresses, you need to understand the risks. Searching for "index of prison break season 4 !FULL!" is a walk through a digital minefield.