Which rootkit replaces regular application binaries with a fake Trojan or modifies the behavior of existing applications by injecting malicious code?

Which rootkit replaces regular application binaries with a fake Trojan or modifies the behavior of existing applications by injecting malicious code?

• A. Application Level/User Mode Rootkit
• B. Library Level Rootkits
• C. Hardware/Firmware Rootkit
• D. Hypervisor Level Rootkit

Answer: (A)

This question tests how a rootkit can covertly take control by operating within the normal user-space environment. When an attacker replaces a regular application binary with a fake Trojan or injects malicious code into an existing application, they’re acting at the application level in user mode. The malicious code runs with the same privileges as the target program, and because it sits in user space, it can intercept or alter the program’s behavior, steal data, or hide activity while still appearing legitimate to basic checks that don’t probe deeper into kernel boundaries. This is why the scenario fits the application level (user mode) rootkit category. Library-level rootkits would tamper with shared libraries loaded by programs to influence behavior, rather than swapping an entire executable, so they’re a different approach. Hardware/firmware rootkits live in firmware or hardware components, not within the OS’s user-space applications. Hypervisor-level rootkits operate from a virtualization layer, affecting the guest environment rather than just replacing a single binary in the host OS.

This question tests how a rootkit can covertly take control by operating within the normal user-space environment. When an attacker replaces a regular application binary with a fake Trojan or injects malicious code into an existing application, they’re acting at the application level in user mode. The malicious code runs with the same privileges as the target program, and because it sits in user space, it can intercept or alter the program’s behavior, steal data, or hide activity while still appearing legitimate to basic checks that don’t probe deeper into kernel boundaries. This is why the scenario fits the application level (user mode) rootkit category.

Library-level rootkits would tamper with shared libraries loaded by programs to influence behavior, rather than swapping an entire executable, so they’re a different approach. Hardware/firmware rootkits live in firmware or hardware components, not within the OS’s user-space applications. Hypervisor-level rootkits operate from a virtualization layer, affecting the guest environment rather than just replacing a single binary in the host OS.