Today, in this
article, we will focus on various methods that are implemented by an attacker to
evade their detection by hiding artifacts in the victim’s system in order to execute
their malicious intent.
Table of Content
·
Introduction
·
Hiding
Files and Directories
o
Using
Command Prompt
·
Hiding
System Users
o
Using
Command Prompt
o
Using
Registry Edit
·
Hiding
File Systems
o
Over Command
Prompt
o
Using
Registry Edit
o
With Disk
Management
·
NTFS File
Attributes
o
Using
Command Prompt
·
Detection
Introduction
An artifact can
simply be defined as an important system file, which thus includes
documentation, test plans, images and even some executable modules.
Operating Systems have a feature to hide these artifacts, in order to
avoid disrupting user work environments and prevent users from changing files
or features on the system. However, an attacker can abuse these functionalities
in order to carry out his evil intents by hiding up these artifacts which thus
provides a clear path to evade his detection.
Let’s try to understand
the above statement by taking a simple example.
Suppose an attacker
penetrates your machine and got a session enabled with that, which thus allows him to exploit your system. The very
first thing that the attacker would do, is that he would create a hidden file and hide his payload, as by exploiting the operating system’s feature i.e. hiding artifacts. Once the attacker has his payload hidden, now he can
carry that out for his malicious intent by tricking up the system
administrator.
With that said,
let’s have a look at the various approaches that the attackers take to evade
their presence.
Hiding Files and Directories
Attackers may set
files or directories to be hidden to evade detection mechanisms.
Let’s boot into our
command prompt by running it as an administrator.
Further, we’ll create up a folder over at our directory, as in our case I’ve
done it as ignite at Desktop. The same can be confirmed
by running the dir command.
In order to hide the file which we have just
created, simply run the following command:
attrib +h +s +r ignite
Okay!! The file has
been hidden now, but wait, let’s see how to unhide the same, simply run the
following command:
attrib -s -h
-r ignite
Great!! From the
below screenshot we can see that as we hit the “dir” command we
got our file back over onto the Desktop.
Hiding Users
Adversaries may use
hidden users to mask the presence of user accounts that they create. In this
section, we will have a look at how users can be hidden.
Using Command Prompt
So let’s reboot
into our command prompt and create a user as in our case we have named it as “ignite”.
A user can be created by using the command: net user ignite /add.
Now, that the user
has been created we need to activate it, which can be done by running the
command: net user ignite /active:yes
We will hide the
user “ignite” by running the command: net user ignite
/active:no
To check the
changes, we would simply restart our PC and notice that our user is no more
visible on the sign-in page.
So, to unhide
the user, simply re-run the command: net user ignite /active:yes as shown earlier.
We’ll notice that our
user “ignite” is again visible over at our sign-in page.
Using Registry Editor
This method can be
lengthier as compared to the above one, but it’s always good to know. So, let’s
explore this path and hide our user.
Over at the Run
Window, type “Regedit” in the search prompt
Once we enter the
registry edit, just navigate to HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Winlogon
Now, that we have
navigated to the path mentioned above let’s Right-click on Winlogon -> Select
New and choose Key
After completing
the above process, we will rename the new key created as “SpecialAccounts”.
Then, right-click
on SpecialAccounts -> Select New and choose Key. We’ll rename this key as “UserList”.
We can see that we
have created two new keys. One is “SpecialAccounts” under Winlogon
and the second key is “UserList” under “SpecialAccounts”.
Over at the blank right-hand
side, follow up as:
Right-click ->
Select New -> Select DWORD (32-bit) Value as shown below
The new key created
should be named as the user we are supposed to hide. In our case, we have named
the new key as “ignite” as we
are hiding this user.
Now, close your
registry editor and restart your PC to see the changes. The user is now invisible.
In order to unhide
the same user, we’ll just go back to our registry editor and navigate to HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Winlogon\SpecialAccounts\UserList.
Then, we’ll double click on the ignite user and change the Value data from 0 to 1 and,
hit enter
Again, restart your
system to see the changes. Your user is back on the sign-in page.
Hiding File Systems
Adversaries may use
a hidden file system to conceal malicious attacks from users and security
tools. File systems provide a structure to store and access data from physical
storage. So, lets’ deep dive and have a look at how the above is accomplished.
Method
1: Over Command Prompt
Let’s say we have an E drive which we want to
hide.
Open disk partition
into your command prompt with as “diskpart”
Let’s now list all
the volumes available there using “list volume”
As the volumes are
over at our screen, let’s choose the volume which contains the drive that needs
to be hidden. In our case, we select volume 3 by running the command: select
volume 3
Great!! We’re
almost there, now to hide the drive, simply run the command:
remove letter
e
From the below screenshot we can see that
Drive E is successfully hidden.
Further, to unhide the drive simply run the
command “assign letter e”.
Method
2: Using Registry Editor
For this method, we’ll
go back into the registry editor as explained in the “Hidden User” section and
navigate to HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
After navigating to
the above-mentioned path, Right-click over on Explorer -> Select New ->
DWORD (32-bit) Value as shown below.
A new key will be
created which needs to be renamed as “NoDrives”
Now, that our new
key has been renamed as “NoDrives”, let’s double click on it and change
the base from Hexadecimal to Decimal and give input to the Value Data field
according to the drive which we wish to hide.
In our case, as we’re
hiding the E drive, we will set the
Value data to “16” as the decimal value of the alphabet E is 16.
You can set it according to yours.
Reboot your system
again, and check for the drives.
Great!! From the
below screenshot you can see that our drive has been hidden now.
To unhide the
drive, navigate back to “Regedit” as explained above and move to HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer.
Right-click on “NoDrives” and just Delete it. Again, restart your system and see that the drive is again visible.
Method
3: Using Disk Management
Let’s open Disk
Management by running the command “compmgmt.msc” in the RUN
WINDOW as shown below.
We’ll select the
drive which we want to hide and right-click on it.
Then select “Change
Drive Letters and Paths”.
After completing
the above step, we’ll select the drive and click on the “Remove” button.
Reboot your system
and you’ll notice that the drive is now hidden. In our case, drive “E” is not visible as we can see
below.
Let’s unhide the drive by going back to
disk management. Double click on New Volume and, select “Change Drive Letter
and Paths”. Click on the Add button and add the drive you wish to by
selecting “Assign the following drive letter” option and press ok.
NTFS File Attributes
Adversaries may use
NTFS file attributes to hide their malicious data to evade detection. Every New
Technology File System (NTFS)
formatted partition contains a Master File Table (MFT) that maintains records for every file/directory on the
system. Let’s explore how the above attack can be executed.
Boot up your
Command Prompt again as an administrator in order to generate up a file with
some data in it:
echo Welcome
to ignite Technologies > file.txt.
From the below
image, we can see that our file has been created with the data we entered.
Now, let’s create
another file inside file.txt but this time we’ll make it as hidden with
echo Join Our
Training Programs > file.txt:hidden
From the below
screenshot we can see that the file “hidden” is not visible at
all.
Go ahead and type
the command: type file.txt:hidden and hit Enter. You will notice
that the file is still not visible to us.
But how to check
the contents?
Simply run the
command as more < file.txt:hidden and you will be there again.
Detection
The following
methods can be used to detect such type of attacks:
·
Monitoring
processes, and command-line arguments for actions indicative of hidden
artifacts.
·
Monitoring
event and authentication logs for records of hidden artifacts being used.
·
Monitoring
the file system and shell commands for hidden attribute usage.
Source
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