PEN-200 Practice Test 4 — 10 Questions

Question 1

During a red team engagement, a tester writes a C# loader that calls the Win32 API function VirtualAllocEx to allocate memory in a remote process, writes shellcode, and creates a remote thread. The loader compiles and runs, but the endpoint's EDR blocks it before the remote thread executes. The tester confirms the EDR is hooking user-mode API functions in ntdll.dll. Which approach most directly avoids the user-mode hooks that triggered the block?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Implement direct system calls by reading the syscall numbers from a clean copy of ntdll.dll and executing the syscall instruction directly from the loader's own code.. User-mode EDR hooks are implemented by patching the entry points of functions inside ntdll.dll. Any call that goes through those functions, whether via the kernel32 wrapper or the Nt-prefixed export, passes through the hook. Direct system calls sidestep the problem by placing the syscall instruction in the loader's own code with the correct service number, so execution transitions to kernel mode without touching the hooked ntdll stubs. This is the most reliable way to bypass user-mode hooking without altering system DLLs.

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Add the /DYNAMICBASE:NO linker flag so the loader's base address does not change between runs.

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Replace the calls to VirtualAllocEx and CreateRemoteThread with their NtAllocateVirtualMemory and NtCreateThreadEx equivalents from ntdll.dll.

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Call VirtualProtect on the ntdll.dll .text section to restore the original bytes before invoking the API.

Question 2

During a PEN-200 lab, a penetration tester develops a custom C# loader that allocates memory, writes shellcode, and executes it. Windows Defender's AMSI flags the process when the shellcode buffer is passed to a scanning routine. The tester wants to prevent AMSI from inspecting the buffer at runtime without disabling Defender. Which technique should the tester apply?

Accepted Answer

Use the AmsiScanBuffer function's memory patching to force it to return a clean result.. AMSI scans buffers passed to functions like AmsiScanBuffer; to evade it without disabling Defender, the tester can patch AmsiScanBuffer in memory to return a benign result. This prevents the shellcode from being flagged. Encoding, CFG, or user privileges do not stop AMSI from scanning the buffer at runtime.

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Run the loader under a different user account with limited privileges.

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Base64-encode the shellcode and decode it at runtime before execution.

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Compile the loader with the /guard:cf flag to enable Control Flow Guard.

Question 3

A penetration tester needs to deliver a Meterpreter payload to a Windows target protected by an EDR that performs both static file scanning and behavioral monitoring of process creation. The tester wants to reduce the chance of detection during initial execution while still obtaining a session. Which two techniques most directly reduce detection in this combined scenario? (Choose two.)

Accepted Answer

Spawn the payload by injecting into a legitimate, already-running process such as explorer.exe rather than starting a new process.. The scenario involves two distinct controls: static file scanning and behavioral process monitoring. A custom loader with encrypted shellcode removes recognizable bytes from disk, defeating static signatures. Injecting into an existing trusted process avoids the new-process creation event that behavioral engines monitor, placing execution inside a process already deemed legitimate. Together these address both controls. Renaming, UPX packing, and registry tampering either leave the static bytes intact or generate their own high-signal events.

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Disable Windows Defender real-time protection by modifying the registry before executing the payload.

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Rename the payload executable to svchost.exe and place it in the user's temp directory.

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Compress the payload with UPX and deliver it as a self-extracting archive.

Question 4

An attacker gains a low-privilege shell on a Windows 10 machine and discovers a third-party service named 'DataSync'. The attacker notes that the service runs as SYSTEM and they have 'FILE_WRITE_DATA' permissions on the service executable 'C:\Program Files\DataSync\sync.exe'. Which action is the most direct method to escalate privileges to SYSTEM?

Accepted Answer

Stop the service, replace 'sync.exe' with a malicious payload, and restart the service.. Service binary hijacking is a powerful technique where an attacker replaces a legitimate executable with a malicious one. Since the service runs as SYSTEM, the replaced binary will execute with those high privileges upon the next service start. This method is often more reliable than DLL hijacking because it directly controls the primary execution flow of the service, provided the attacker can restart the service or wait for a system reboot.

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Place a malicious DLL named 'sync.dll' in the 'C:\Windows\System32' directory to intercept calls.

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Modify the service configuration using 'sc config' to point to a different malicious executable.

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Create a new service with the same name in the 'HKCU' registry hive to override the system service.

Question 5

A junior penetration tester is preparing a payload for a Windows 10 target and wants to avoid signature-based detection by changing the binary's appearance without altering its functionality. Which technique is specifically designed to achieve this?

Accepted Answer

Encoding the payload with msfvenom's shikata_ga_nai encoder multiple times.. Shikata_ga_nai is a polymorphic encoder that mutates the payload's bytes while preserving its functionality, directly targeting signature-based detection by changing the binary appearance. The other options either do not alter the binary signature, are easily unpacked, or change only the delivery mechanism rather than the payload's bytes.

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Splitting the payload into multiple chunks and reassembling at runtime.

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Running the payload from a remote SMB share instead of the local disk.

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Compressing the payload with UPX to reduce its size.

Question 6

When reviewing 'sudo -l' output, what does the 'NOPASSWD' tag signify for the listed command?

Accepted Answer

The command can be run as root without entering a password.. The 'NOPASSWD' tag indicates that the user can execute the specified command with sudo privileges without being prompted for their own password. This is a critical misconfiguration, as it removes the authentication barrier for privilege escalation. In an attack scenario, it allows for immediate, automated execution of commands as root, which is significantly more dangerous than configurations that still require a user to authenticate via their password.

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The user is automatically added to the root group.

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The command is not logged by the system administrator.

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The command will run in a sandbox for security.

Question 7

Which command-line tool is primarily used during the reconnaissance phase to identify open ports and service versions on a remote target?

Accepted Answer

Nmap. Nmap is the industry-standard tool for port scanning and service enumeration. By identifying open ports and the software versions running on them, a tester can pinpoint specific vulnerabilities to research. This step is the foundation of the reconnaissance phase, as it maps the target's attack surface and guides the subsequent selection of exploits, ensuring a focused and efficient penetration testing process.

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netcat

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Wireshark

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grep

Question 8

You have compromised a Windows server and want to escalate privileges using the `AlwaysInstallElevated` setting. You check the registry and find that both `HKLM\SOFTWARE\Policies\Microsoft\Windows\Installer\AlwaysInstallElevated` and `HKCU\SOFTWARE\Policies\Microsoft\Windows\Installer\AlwaysInstallElevated` are set to 1. What is the most direct way to leverage this misconfiguration?

Accepted Answer

Create a malicious MSI package and execute it with `msiexec /quiet /qn /i malicious.msi` to run with SYSTEM privileges.. With AlwaysInstallElevated enabled in both registry hives, any MSI package installed by a user runs with SYSTEM privileges. The most direct exploitation is to create a malicious MSI that performs a privileged action, such as adding a user to the Administrators group, and then install it using `msiexec`. This leverages the misconfiguration exactly as designed.

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Leverage the setting to bypass UAC and run any executable as an administrator without an MSI package.

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Use `reg add` to modify the service binary path of a running service to point to a malicious executable.

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Extract the MSI to a writable directory and replace a DLL to achieve privilege escalation.

Question 9

You identify a cron job running as root that executes a script located in a writable directory. What is the most reliable way to escalate privileges in this scenario?

Accepted Answer

Append a reverse shell command to the writable script.. When a cron job runs as root, any script it executes also runs with root privileges. If the script is writeable by a low-privileged user, it can be modified to include a reverse shell. This is a common misconfiguration that highlights the importance of checking file permissions and cron job schedules during the post-exploitation phase of a penetration test or a professional security assessment.

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Modify the /etc/shadow file directly.

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Restart the crond service to force execution.

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Change the ownership of the script using chmod.

Question 10

You are developing an exploit for a 32-bit Windows application that contains a stack-based buffer overflow. After overwriting EIP with a JMP ESP address, you place a payload that includes a reverse shell. During testing, the shell connects back successfully, but the application crashes immediately after the shell terminates. What is the most likely cause of the crash?

Accepted Answer

The shellcode lacks a proper exit sequence, causing the process to execute invalid memory after the shell ends.. The crash after the shell terminates suggests that the shellcode does not properly exit the process. When shellcode completes, it must call a termination function like ExitProcess; otherwise, the CPU continues executing whatever bytes follow, often leading to an access violation. The other options are inconsistent with the observed successful shell connection, which confirms that the overwrite and shellcode execution were correct.

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The offset to EIP was miscalculated, causing the return address to be overwritten with an incorrect value.

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The shellcode was encoded with an XOR encoder that corrupted the payload after execution.

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The JMP ESP address contains a null byte, which truncates the payload during transmission.