VMM Based Rootkit Detection on Android

1. VMM Based Rootkit Detection on Android Class Presentation Pete Bohman, Adam Kunk, Erik Shaw

2. Motivation • Smartphone malware on the rise • Increased security implications (compared to PC) • Sensitive information: GPS, contacts, SMS, call log • Constantly connected to the Internet • Naïve users, limited use of anti-virus protection The Increase of Mobile Malware Variants (2004 – 2010)

3. Defensive Rootkit Approaches • User mode rootkits • Process infection, binary patching, lib hooks • User mode integrity checkers • tripwire, chkrootkit, rkthunter, AV scanner • Kernel mode rootkits • malicious device drivers and LKMs • sys call hooking, kernel data structure manipulation (DKOM) • Kernel level inspection • behavioral analysis, data structure integrity checkers, hook detection • But… Any kernel level inspection mechanisms can be subverted by kernel level rootkits!

4. Our Approach Android Software Stack • Two Pronged • KM security mechanisms • System call integrity checks • Hidden process detection • ACLs for Android personal data • VMM inspection • Ensures integrity of static KM • Isolated from host OS • We exercise a “layer-below” level of security in which we establish trust beneath the kernel

5. Overview • Design • VMM Interface Design • Protection KM Design • Implementation • Results • Demo Presentation • Conclusion • Q&A

6. VMM Interface Design Application Framework Android VMM Libraries and Runtime Linux Kernel 4. Invoke KM Trusted KM <ISR> 2. Validate Protected KM 3. Raise Monitor Interrupt 1. Hardware Timer Interrupt Hardware (Emulator)

7. Protection KM Design Maps Contacts SMS App … Application Framework Content Provider Location Provider Activity Manager Malicious Native Application Libraries and Runtime System Calls Open Socket Read GPS SQL Query Linux Kernel Trusted KM System Call Whitelist Original Sys Call Table Sys Call Table Open

8. Protection KM Design Android VMM Libraries and Runtime System Calls Linux Kernel Trusted KM System Call Whitelist Original Sys Call Table Malicious LKM Sys Call Table Z X Y Linux Kernel <ISR> Monitor Interrupt

9. Implementation • VMM Interface • Implemented VMM security functionality in an emulated hardware device within QEMU • Protected KM data and text compiled into QEMU emulator (VMM) Kernel Image Linux Kernel Source with Protection KM Compilation Protected Text Sect. Protected Data Sect. QEMU Emulator(VMM) QEMU Emulator (VMM) Compilation Protected Text Protected Data

10. Implementation • Protection KM • Checks system service function pointersin sys_call_table • Reports problem and restores them ifthey have been altered • Hooks sys_open and prevents access to mmssms.db and contacts2.db • Unless process name and parent process name are foundin the access control list • Likewise restricts socket and sys_read of GPS data according to the access control list

11. Implementation • Malicious native mode application • Reads contacts database file • Reads GPS location • Transmits data using network sockets • Runs as Linux user mode process, underneath the Android ApplicationFramework • Malicious LKM • Implemented by following the MindTrick Rootkit techniques • Intercepts read system calls to access GPS location • Attempts to access the SMS and contacts database files

12. Results • We are able to detect and correct modifications to the sys_call_table • Malicious LKM system call table hooking was thwarted • Malicious LKM unable to obtain GPS coordinates • We are able to prevent malicious access to sensitive resources • Malicious application fails to read GPS data, fails to open sensitive database files, and fails to open network sockets • Malicious LKM also fails to open sensitive database files • Demo (short): http://www.youtube.com/watch?v=IR9yDyT50HQ • Demo (long): • http://www.youtube.com/watch?v=4M5YgsGU9Bw

13. Conclusion • “Layer-Below” Protection • Security of the Linux kernel must be rooted in a layer below the kernel to withstand kernel level attacks • Trusted “layer-below” protection mechanisms can serve as the secure foundation for enabling additional advanced protection mechanisms in the kernel

14. Questions?

15. Backup – Android Architecture

16. Backup – Protection by Layer

17. Backup – Problem Statement • Rootkit detection and prevention on the Android platform with specific regards to the sensitive resources Android provides. • Kapersky 2011: 1046 unique malware strains targeting mobile platforms • Android platform built on Linux Kernel, a well known target. • Sensitive information on smart phones • GPS, contacts, text messages, call log