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Does iOS 5.1 support a built in firewall like Mac OS X does? Can't see anything about it in Settings.

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Why? What are you trying to accomplish? – jaberg Apr 9 '12 at 14:40
Would be nice to have a Firewall enabled when using a public wifi hot spot, etc. – MrDaniel Apr 9 '12 at 15:41
Again, why? Apps are sandboxed. Un-needed ports are blocked. What specifically are you trying to accomplish? – jaberg Apr 9 '12 at 15:43
Just an extra layer of security, having a iOS device saying I am here and I have ports open does not seem wise – MrDaniel Apr 9 '12 at 15:57
I've had folks at DC612 (the local Defcon SIG) try various scanning tools against my iPhone and they haven't come up with anything useful. Not a definitive answer I realize, but it seems to me you're chasing dragons. Best of luck. – jaberg Apr 9 '12 at 16:15
up vote 9 down vote accepted

Yes, there is a Firewall, but not an easily accessible one. All ports are dynamically blocked on iOS to incoming traffic until an app needs specific access (and iOS handles this all by itself (and an outside app cannot request access)). In a back-door sort of way, it's accessible to the user, but there's no way of changing the tables without Jailbreaking. If you do, however, require to have your tables modified, I've answered a similar question here that explains how.

Edit/Update/Disclaimer: I'm not so sure how accurate this information is; coming back 2.5yrs later, knowing more than I did then, I actually don't believe that iOS has a firewall. The OS just doesn't listen on any ports that it doesn't need to listen on and everything else is just passively blocked (just like other operating systems).

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How did you find out about "All ports are dynamically blocked on iOS to incoming traffic until an app needs specific access" – MrDaniel Apr 16 '12 at 21:07
If you scan your iOS device with a network scanner, you shouldn't find any open ports. If you turn on SSH or any other tool that needs to listen on a specific port, and then scan your device, you'll see that the port is now open. This also makes your device more defensive against DoS attacks. – Andrew Larsson Apr 16 '12 at 22:02

When you have jail broken your iPhone/iPod/iPad you can download a firewall setting in cydia

You can find an article about it here:

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Welcome to Ask Different, Xcodeuser!! Thanks for posting an answer. Can you please add a little more information, such as a link to the firewall setting tweak? Thanks! – daviesgeek Apr 9 '12 at 16:12

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