A special file system structure made with intention of breaking bad bots
It is made in the way that causes the bot to browse recursive symlink structure slowing it down in the process where it's left preocuppied with that and that takes long enough before it can traverse the other content of the site. An example file structure is shown below, the directory containing such items must be excluded using robots.txt and link must not be shown to regular visitors and proper bots (hidden, witdth/height with value of 0, nofollow tag, etc)
files/misc/test -> ../..
secret/less/stuff -> ../more
secret/more -> ..