Find conditions on the model without a new method

I've recently implemented an "active" flag on several of my models in
a very large codebase, and I'd rather not have to go back and change
every Model.find() instance to specify the new conditions - {:active
=> true}

So I was thinking: how can I make the model itself automatically
append that to the conditions passed in?

I tried this, but to no avail:
(in app/models/model.rb)
Class Something < ActiveRecord::Base

# ...

  # Overwriting the find method to exclude anything NOT active.
  def find
    if @conditions.blank?
      @conditions = "active = true"
      @conditions = @conditions + " AND active = true"


# ...

Unfortunately, my tests didn't work. I went in and set the first row
in my somethings table to be inactive, but find(:first) still returned

I don't see an activerecord call back like "before_find" or something
(though I've read about, but can't seem to find documented, an

Does anyone know how I can do this, or is manually editing every
single Model.find instance the only way?

I think default_scope will do what you want here.
For each model:
default_scope :conditions => {:active => true}

I am not sure at which version of rails default_scope was introduced.