Positive security model (code modification prevention)

= Context = Mobile app developers must take into account a whole host of new risks that relate to hosting code in an uncontrolled environment. If you are hosting code in an untrustworthy environment, you are susceptible to the risk that an adversary will reverse engineer and modify your code via binary attacks &#91;1&#93; &#91;2&#93; &#91;3&#93; &#91;4&#93;.

This content is part of a much bigger set of principles defined within the Architectural Principles That Prevent Code Modification or Reverse Engineering project.

= Description = A "positive" integrity security model applies integrity controls to protect code and data based on characteristics that are known and good, rather than what is known to be bad. This reduces the amount of maintenance involved in maintaining integrity controls within the application over time.

= Examples = For example, a value-verification integrity control should verify that a data element holds particular values when it needs to verify that the application has not been tampered with. It should not look for known bad values as these values may grow over time with new, unknown avenues of attack.

= External References = [1] Arxan Research: State of Security in the App Economy, Volume 2, November 2013:
 * “Adversaries have hacked 78 percent of the top 100 paid Android and iOS apps in 2013.”

[2] HP Research: HP Research Reveals Nine out of 10 Mobile Applications Vulnerable to Attack, 18 November 2013:
 * "86 percent of applications tested lacked binary hardening, leaving applications vulnerable to information disclosure, buffer overflows and poor performance. To ensure security throughout the life cycle of the application, it is essential to build in the best security practices from conception."

[3] North Carolina State University: Dissecting Android Malware: Characterization and Evolution, 7 September 2011:
 * “Our results show that 86.0% of them (Android Malware) repackage legitimate apps to include malicious payloads; 36.7% contain platform-level exploits to escalate privilege; 93.0% exhibit the bot-like capability.”

[4] InfoSecurity Magazine: Two Thirds of Personal Banking Apps Found Full of Vulnerabilities, January 3 2014:
 * “But one of his more worrying findings came from disassembling the apps themselves ... what he found was hardcoded development credentials within the code. An attacker could gain access to the development infrastructure of the bank and infest the application with malware causing a massive infection for all of the application’s users.”