This article provides a comprehensive theoretical overview of Linux rootkits, exploring their taxonomy, evolution, and the sophisticated hooking techniques used to subvert the operating system kernel. It defines rootkits as stealthy malware designed for persistence and evasion, distinguishing between user-space implementations that hijack libraries and kernel-space variants that operate with maximum system privileges. The text highlights the shift from historical methods to modern approaches necessitated by hardening efforts in contemporary Linux distributions.
The content details the technological progression of rootkits over the last two decades, moving from simple Shared Object (SO) injection to Loadable Kernel Modules (LKM), and eventually to advanced techniques leveraging eBPF and io_uring. This evolution reflects a constant cat-and-mouse game between attackers and defenders, where new kernel interfaces designed for performance or observability are repurposed to bypass traditional security monitoring and syscall auditing.
Finally, the analysis dives into specific hooking mechanisms such as Interrupt Descriptor Table (IDT) hooking, syscall table patching, and inline function patching. It discusses the impact of recent architectural changes, such as the syscall dispatch shift in Linux kernel 6.9, and introduces emerging techniques like FlipSwitch that demonstrate how adversaries continue to find ways to maintain control in increasingly hardened environments.
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