Spambots are designed to mimic humans but since the content posted by these bots is often created by humans there tends to be minimal effort put into that content. Hallmarks are 1 or 2 line questions with keyword anchor text links. It’s a dead giveaway when the signature is made up of two similar keywords pointing to the identical URL. While they could be cheap human labor that is mimicking spambot activity, does it make a difference?
There are other signs like never replying to questions or only replying with generic responses that do not address any particular reply within the thread. When you see a member account that has posted nothing but this type of content than you have to conclude that they are not really adding anything of value to the forum, they are just there to get backlinks with the least amount of effort, just enough to prevent having their threads deleted.