In my opinion, Q&A is more effective in combating spam and should be set as the default.
Why?
The default plugin is very old, exists since the beginning of phpBB3, has long since was broken and isn't intended to prevent spambot. Is possible to read various topics about 'violent' attacks of spam in Support Forum, the fault of the inefficiency default plugin.
How?
Since the phpBB is translated into several languages, I think that new text variables should be entered with questions and answers, which must be translated, adapted or changed(according to choice of the translators).
Benefits
Better combating spam bots.
Thoughts?
EDIT: Ticket