Exposing assets in development and production in Rails 3.2

Question

I have a legacy Rails 3.2 app and if I have a JavaScript file at:

app/assets/javascripts/jt.js

I'm able to access it at

https://dev-platform.domain.com/assets/jt

We are using the asset pipeline and I'm not sure why this is available. It seems like something in assets/javascripts or assets/styles will show up. Is this the intended behavior? How can I prevent this?

Here's my Gemfile#assets

group :assets do
  gem 'coffee-rails', '3.2.2'
  gem 'font-awesome-sass', '4.7.0'
  gem 'foundation-rails', '6.1.2.0'
  gem 'jquery-rails', '3.1.4'
  gem 'jquery-ui-rails', '5.0.5'
  gem 'sass-rails', '3.2.6'
  gem 'turbo-sprockets-rails3', '0.3.14'
  gem 'twitter-bootstrap-rails', '2.2.8'
  gem 'uglifier', '2.7.2'
end