In this lesson,
we're going to cover the concept of Payload Obfuscation,
and the tools used to implement,
such as PowerShell, PsExec, and Evil-WinRM.
Payload Obfuscation, refers to techniques
used to disguise malicious payloads
to avoid detection by security tools,
such as antivirus software,
intrusion detection systems,
and endpoint protection platforms.
The primary goal is to make the payload less recognizable
by altering its appearance
without changing its functionality.
This technique is crucial for attackers
who want to ensure their payloads can be delivered
and executed successfully on a target.
To understand payload obfuscation,
let's first look at what constitutes a payload
in a context of pentesting.
A payload is a piece of code
that executes a specific function
once delivered to the target system.
This could include anything from a reverse shell,
which provides remote access to the attacker
to ransomware scripts
that encrypts files on the victim's machine.
Obfuscation can be achieved through various methods,
including encoding, encryption, compression,
and code manipulation.
Encoding involves changing the payload's appearance
by converting it into a different format,
such as Basic64 encoding.
Encryption involves encrypting the payload
so that it appears as random data
until it is decrypted at runtime.
Compression involves compressing the payload
to change its binary structure.
Code manipulation involve modifying the code structure
by inserting junk code, renaming variables,
or changing the control flow.
PowerShell can be used to obfuscate payloads.
By leveraging PowerShell,
attackers can encode, compress, or encrypt their payloads.
Here's an example of encoding a PowerShell payload
using Base64.
Now, in this example,
the original payload is converted to Base64 string,
which can then be decoded
and executed on a target system.
This obfuscation technique,
helps to bypass simple string-based detection mechanisms.
Next, we have PsEec,
which is a tool that allows for remote execution
of processes on other systems.
It can be used in conjunction with PowerShell to deliver
and execute obfuscated payloads on remote machines.
Here's how you might use PsExec
to run an obfuscated PowerShell script on a remote machine.
In this command, the PsExec connects to the remote computer,
named \\remote-computer,
and uses the -s flag to run the command
as the system account,
it then starts powershell.exe
and executes a PowerShell command specified by -Command.
The actual PowerShell command being run is an encoded script
indicated by the -EncodedCommand
$encodedPayload option,
which allows the execution of complex
or obfuscated scripts on the remote system.
Lastly, we have Evil-WinRM.
Evil-WinRM is another tool commonly used
in penetration testing,
especially for interacting
with Windows Remote Management or WinRM services.
This tool can be used to execute obfuscated payloads
on a target system.
Here's an example of using Evil-WinRM
to execute a Base64 encoded PowerShell payload.
This command uses evil-winrm
to connect to a remote Windows computer
via the Windows RM or Windows Remote Management Service.
The -i remote-computer specifies the target machine.
The -u username and -p password parameters
provide the credentials needed to log in.
Now, once connected,
it executes a PowerShell command
specified by the - s "powershell
EncodeCommand $encodePayload",
which runs an encoded PowerShell script
on the remote system.
to execute complex scripts
while maintaining a secure connection to the target machine.
So remember, payload obfuscation
is a critical aspect of penetration testing.
It involves techniques to discuss malicious payloads
to avoid detection while security tools.
Tools like PowerShell, PsExec, and Evil-WinRM
are commonly used for this purpose.
Understanding these techniques allow penetration testers
to better secure their payloads
and ensure successful execution on target systems.