Adversaries may download and execute dynamic code not included in the original application package after installation. This technique is primarily used to evade static analysis checks and pre-publication scans in official app stores. In some cases, more advanced dynamic or behavioral analysis techniques could detect this behavior.

However, in conjunction with Execution Guardrails techniques, detecting malicious code downloaded after installation could be difficult. On Android, dynamic code could include native code, Dalvik code, or JavaScript code that utilizes Android WebView’s JavascriptInterface capability. On iOS, dynamic code could be downloaded and executed through 3rd party libraries such as JSPatch.