If you develop an app, someone is going to try to destroy it. Once upon a time, hackers may have had a reason for trying to destroy your hard work, but these days the only motivation computer outlaws need is a little boredom. Thankfully Apple has released a Secure Coding Guide for developers old and new alike, which provides an invaluable resource for building an app that can survive attacks.
As the recent SnapChat leaks have shown, leaks or hacks don't have to cause constant damage to harm a program. Sometimes a single break-in is enough. Apple makes this point clearly during the Coding Guide's introduction.
A large-scale, widespread attack is not needed to cause monetary and other damages; a single break-in is sufficient if the system broken into contains valuable information. Although major attacks of viruses or worms get a lot of attention from the media, the destruction or compromising of data on a single computer is what matters to the average user.
For your users' sake, you should take every security vulnerability seriously and work to correct known problems quickly. If every Macintosh and iOS developer follows the advice in this document and other books on electronic security, and if the owner of each Macintosh takes common-sense precautions such as using strong passwords and encrypting sensitive data, then OS X and iOS will maintain their reputations for being safe, reliable operating systems, and your company's products will benefit from being associated with OS X or iOS.
It's easy to get cocky when using OS X or iOS products; after all they're notoriously reliable and don't face normal PC's history of hacking vulnerability. The Secure Coding Guide will teach you the different types of security vulnerabilities that commonly effect iOS apps.
Apple has even provided a handy Security Development Checklist to run down before you submit your final product to the App Store.
You can find Apple's Secure Coding Guide as a free PDF download right here.