Disable the “Are you sure you want to open this file?” warning dialogue in Mac OS X
“Blahblah is an application downloaded from the internet. Are you sure you want to open it?”
Starting in Mac OS X Leopard, you may have noticed that when you download a file from the web and go to open it, you will get a prompt saying something along these lines.
This is Mac OS X just being safe, but if you always know for sure what you’re downloading it could even be overly safe. You can disable this quarantine message by launching the Mac Terminal and typing the following command:
defaults write com.apple.LaunchServices LSQuarantine -bool NO
You will then need to reboot (although killing the Finder should work as well) for the changes to take effect. To reverse this and get the file quarantine message back, type:
defaults write com.apple.LaunchServices LSQuarantine -bool YES
Again you will need to reboot (or kill the Finder) to have the changes back.

Or, you could ask the developer to “sign” their apps so everyone is a little safer.
http://developer.apple.com/mac/library/documentation/Security/Conceptual/CodeSigningGuide/Introduction/Introduction.html
thats cool, but how about some code to disable the “Are you sure you want to restart your computer now?”
That and the Shut Down warning also.
Or at least a command to reduce the timer from 1 minute to 5 seconds or something
Yes! I find this very annoying and Un-Mac like to be so annoying. The shutdown timer makes some sense even though that is too long. The restart timer is absurd. Oh, let me think about it for 1 min to see if I really wanted to restart. Should be 10 seconds at most.
@MilkyTech
Hold down option when choosing restart or shut down. Doing so will eliminate the dialog box that normally appears.
but I want to eliminate it permanently, not just for 1 instance
You can immediately shut down your MacBook Pro for example by using the following simultaneous key sequence:
Control Option Command Eject
Have fun!
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[...] Remember this method only effects items you choose to specify. If you want to disable this message from ever appearing again for any applications downloaded, learn how to permanently disable the file warning dialogue. [...]
[...] Disable the “Are you sure you want to open this file?” warning dialogue in Mac OS X. [...]
To Shut Down (or Restart, or Sleep for that matter) without the ridiculous waiting period that Apple imposes on you, go to the “Keyboard” Preference Pane in System Preferences, click on the “Plus” sign at the bottom, copy the Menu Title you want (without the ellipses, of course), thusly – - “Shut Down”, or “Restart”, or “Sleep”.
Make sure the Application drop-down menu is set to “All Applications”. I always make the keyboard shortcut itself into something hard to hit by accident, but fairly easy to access (and not used by other apps), like “Shift-Opt-Command F1″. Restart and enjoy!
Thank you. This helps.
Every time I log in, this happens for dropbox, and the command in terminal doesn’t work
I was looking for this for a while now, Thank you for posing.
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[...] of malware. Apple didn’t seem to mind that the DB will continue to collect data even after file quarantine was turned off for files and [...]