How to add an extra registration question to frustrate human-assisted bot registration?

AdminCP -> User Profile Fields -> Add New User Profile Field

Profile Field Type: Single-Line Text Field
<<Continue>>

Use the following information when creating the Profile Field:

Title: Anti-spam Protection


Description: Enter the first character of the word "Monkey"
(Note: Adjust the title to the question you want to ask)


Default Value: sausages
(Note: can anything except a valid answer!)

Field Required: Yes, at registration and profile updating
Field Editable by User: Only at registration
Private Field: Yes
Field Searchable on Members List: No
Show on Members List: No

Regular Expression: ^[mM]$

Ahh regex, bane of my life. The above allows either upper or lowercase M/m as an acceptable answer. Similar can be done with words e.g. ^yes|YES$

/^m$/i

I fucking hate regex