!epthook (hidden hook with EPT - stealth breakpoints)
Description of the '!epthook' command in HyperDbg.
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Description of the '!epthook' command in HyperDbg.
Last updated
!epthook
!epthook [Address (hex)] [pid ProcessId (hex)] [core CoreId (hex)] [imm IsImmediate (yesno)] [buffer PreAllocatedBuffer (hex)] [script { Script (string) }] [asm condition { Condition (assembly/hex) }] [asm code { Code (assembly/hex) }] [output {OutputName (string)}]
Puts a hidden breakpoint (0xcc) on the target function in user-mode and kernel-mode without modifying the content of memory in the case of reading/writing.
If you want to keep the current context without continuing the debuggee, you should use the '' command instead.
[Address (hex)]
The Virtual address of where we want to put the hook.
[pid ProcessId (hex)] (optional)
Optional value to trigger the event in just a specific process. Add pid xx to your command; thus, the command will be executed if the process id is equal to xx. If you don't specify this option, then by default, you receive events on all processes.
Still, in the case of user-mode debugging, HyperDbg will apply it only to the current active debugging process (not all the processes). In that case, you can specify pid all to intercept events from the entire system.
[core CoreId (hex)] (optional)
Optional value to trigger the event in just a specific core. Add core xx to your command thus command will be executed if core id is equal to xx. If you don't specify this option, then by default, you receive events on all cores.
[imm IsImmediate (yesno)] (optional)
Optional value in which yes means the results (printed texts in scripts) should be delivered immediately to the debugger. no means that the results can be accumulated and delivered as a couple of messages when the buffer is full; thus, it's substantially faster, but it's not real-time. By default, this value is set to yes.
[buffer PreAllocatedBuffer (hex)] (optional)
[script { Script (string) }] (optional)
[asm condition { Condition (assembly/hex) }] (optional)
[asm code { Code (assembly/hex) }] (optional)
[output {OutputName (string)}] (optional)
As the Context ($context pseudo-register in the event's script, r8 in custom code, and rdx in condition code register) to the event trigger, HyperDbg sends the virtual address of where put the hidden hook's breakpoint.
This event supports three debugging mechanisms.
Break
Script
Custom Code
Imagine we want to put a hook on fffff800`4ed6f010, this will break into the debugger when the target address hits and gives the control back to you.
Alternatively, you can use nt!ExAllocatePoolWithTag too.
You can also use an expression like nt!ExAllocatePoolWithTag+@rcx+5 too.
The above command when messages don't need to be delivered immediately.
Script (From File)
If you saved your script into a file, then you can add file: instead of a script and append the file path to it. For example, the following examples show how you can run a script from file:c:\users\sina\desktop\script.txt.
Run Custom Code (Unconditional)
Or if you want to use assembly codes directly, you can add an asm before the code.
Run Custom Code (Conditional)
Or if you want to use assembly codes directly, you can add an asm before the condition and also before the code.
Keep in mind that a conditional event can be used in Breaking to Debugger and Running Script too.
Use HIDDEN_HOOK_EXEC_CC as EventType, and send the address of where you want to hook in OptionalParam1in DEBUGGER_GENERAL_EVENT_DETAIL.
This command is much slower than !epthook2, because it cause vm-exits, but on the other hand, this implementation doesn't have any limitation. For example, you can use this command for hooking user-mode while you can't use !epthook2 on user-mode.
You shouldn't use any of !monitor, !epthook, and !epthook2 commands on the same page (4KB) simultaneously. For example, when you put a hidden hook (!epthook2) on 0x10000005, you shouldn't use any of !monitor or !epthook commands on the address starting from 0x10000000 to 0x10000fff.
You can use !epthook (just !epthook not !epthook2 and not !monitor) on two or more addresses on the same page (means that you can use the !epthook multiple times for addresses between a single page or putting multiple hidden breakpoints on a single page). But you can't use !monitor or !epthook2 twice on the same page.
Post-Nehalem Processor (EPT)
Processor with Execute-only Pages Support
Optional value which reserves a safe to be accessed within the event codes.
A HyperDbg will be executed each time the event is triggered.
Optional assembly codes which check for in assembly.
Optional will be executed each time the event is triggered.
Optional output resource name for .
This event does not support '', as this mechanism won't make sense for the function hooks. If you want to change the execution path (e.g., ignoring a function call), you can directly manipulate the RIP register.
This event does not support . Due to the nature of function hooking implementing calling stages in this context wouldn't be meaningful.
Please read "" if you need a conditional event, a conditional event can be used in all "Break", "Script", and "Custom Code".
Using the following command, you can use HyperDbg's Script Engine. You should replace the string between braces (HyperDbg Script Here) with your script. You can find script examples .
You can use to forward the event monitoring results from this event and other events to an external source, e.g., File, NamedPipe, or TCP Socket. This way, you can use HyperDbg as a monitoring tool and gather your target system's behavior and use it later or analyze it on other systems.
Please read "" to get an idea about running a custom buffer code in HyperDbg.
Your custom code will be executed in vmx-root mode. Take a look at for more information. Running code in vmx-root is considered "".
Putting a hook on fffff801deadbeef and run 3 nops whenever the hook is triggered. Take a look at for more information.
Putting a hook on fffff801deadbeef and run 3 nops whenever the hook is triggered and also 3 nops condition. Take a look at and for more information.
This command uses the same method to .
Take a look at "" to see how does it work.
This command cannot be used simultaneously with the '' command.
This command creates an . Starting from HyperDbg v0.7, events are guaranteed to keep the debuggee in a halt state (in the ); thus, nothing will change during its execution and the context (registers and memory) remain untouched. You can visit for more information.