Detecting patching of executables without system calls

Popular software applications (e.g. web browsers) are targeted by malicious organizations which develop potentially unwanted programs (PUPs). If such a PUP executes on benign user devices, it is able to manipulate the process memory of popular applications, their locally stored resources or their environment in a profitable way for the attacker and in detriment to benign end-users. We describe the implementation of a tamper detection mechanism based on code selfchecksumming, able to detect static and dynamic patching of executables, performed by PUPs or other attackers. As opposed to other works based on code self-checksumming, our approach can also checksum instructions which contain absolute addresses affected by relocation, without using calls to external libraries. We implemented this solution for the x86 ISA and evaluated the performance impact and effectiveness. The results indicate that the run-Time overhead of selfchecksumming grows proportionally with the level of protection, which can be specified as input to our implementation. We have applied our implementation on the Chromium web-browser and observed that the overhead is practically unobservable for the end-user.