It doesn't matter because it won't help much, if at all. The script kiddies are running scripts that check for known files in several popular CMSs, so unless the plugin makes major changes to WP's behaviour, WordPress will still be findable.
The first time it happened, I just deleted the file and went forward. The second time, I just deleted the app. I know I could write a script to deal with this, but it was just a test, playground type app. All it did was make me say I needed to move my "blog" off WordPress and stop trying to host Rails apps on Webfaction.
PS: The domain the Rails app was on had never hosted a WP site ever before. WP is just so ubiquitous that that they were just trying to hack any site -- even one that had like 3 organic visitors ever.