Course 42 - Mobile Malware Analysis Fundamentals | Episode 8: Static Analysis of Android Banking Trojans

Android Basic Static Analysis — Advanced Study GuideThis episode demonstrates how to perform basic static analysis of Android applications, moving from initial malware triage to manifest analysis, code decompilation, and identification of suspicious functionality.1. Android Malware Analysis MethodologyAlthough Android and iOS have very different architectures, the fundamental malware-analysis methodology remains similar:Sample ↓ Identification ↓ Hashing ↓ Threat Intelligence ↓ Manifest Analysis ↓ Code Analysis ↓ Behavioral Hypothesis ↓ Dynamic Analysis The objective of static analysis is to understand as much as possible without executing the malware.2. Initial APK IdentificationThe first stage is to establish basic information about the APK.Useful checks include:File typeFile sizeCryptographic hashesExisting antivirus detectionsKnown threat intelligenceFor example:file "malware 2.apk" Hashing provides a stable identifier for the sample:md5sum "malware 2.apk" sha256sum "malware 2.apk" The resulting hashes can then be searched in authorized malware-intelligence services such as VirusTotal.Important principleA clean scan does not establish that an APK is safe. Static analysis should continue even when existing security engines report no detection.3. AndroidManifest.xml AnalysisThe AndroidManifest.xml is one of the most important artifacts in an Android investigation.An APK's manifest is normally stored in a compiled/binary representation, so tools such as apktool can be used to decode it into a human-readable form.For example:apktool d "malware 2.apk" -o malware_analysis The decoded project may contain:malware_analysis/ ├── AndroidManifest.xml ├── smali/ ├── res/ ├── assets/ └── ... The manifest can reveal:Application componentsActivitiesServicesBroadcast receiversContent providersIntent filtersRequested permissionsExported components4. Permission AnalysisPermissions can provide an early indication of an application's intended capabilities.In this lab, the APK requests permissions associated with:Reading SMSWriting SMSReceiving/intercepting SMSInstalling packagesRemoving packagesThis combination is particularly interesting for a purported banking application.However, permissions alone do not prove malicious behavior.A better analytical question is:Which parts of the code actually use these permissions, and for what purpose?That connects manifest analysis with code analysis.5. Identifying the Application's TargetThe investigation decodes the application's string resources and discovers that its name translates from Korean to "smart banking."This provides an important contextual clue.Combined with the SMS-related permissions, the analyst can begin developing a hypothesis:Korean Banking Theme + SMS Access + Device Information ↓ Potential Banking-Focused Malware The hypothesis should then be tested against the application's actual code and behavior.6. DEX AnalysisAndroid applications typically contain compiled code in DEX (Dalvik Executable) format.The primary file is often:classes.dex Static analysis can involve converting DEX bytecode into a more readable representation.A traditional workflow demonstrated in the episode is:classes.dex ↓ dex2jar ↓ JAR / Java representation ↓ JD-GUI / JEB / Procyon ↓ Pseudo-source code The resulting code is not necessarily identical to the original source code, but it can provide a useful approximation of the application's logic.7. Why Decompilation MattersManifest analysis tells you what the application declares.Decompilation helps determine what the application actually does.For example:Manifest: READ_SMS RECEIVE_SMS ↓ Code: SMSReceiver ↓ Extract SMS...