defender-control

currently a work in progress - feel free to come back to check on any updates

what is this project?

We all know that disabling windefender is a pain going through countless registries.
The next easiest solution is to use freeware and currently the most popular one is by sordum. (i won't link here - you can find it on the first google result) however, i was first wary of this program and the virus total detections; althought they are claimed to be false positive. but i know that this program has worked well for me and friends in the past.

but for those who like open source, i took apart this program and did the research to disable windows defender in an easy open source manner without having to worry about running malware.

reversal

Our tool of choice will be IDA & x64 debugger for this task
firstly we are going to inspect the strings and look for anything interesting.
Strings seems to be hidden in this one, so I will do 2 different PoC of attack.
The first one, is to hook the registry functions and output their arguments. Since I know
for a fact after looking at the imports - this program works by writing into relevant registries.

The second method is to breakpoint each function with x64 debugger and take a look at the strings on runtime.

I did eventually come up with a third method, and it was to let procmon do its thing while you debug the program - but ill leave that as an exercise for another day.

x64 Debug

disabling defender

If we breakpoint onto RegSetKeyValue it writes into "DisableAntiSpyware" which we can research on the internet
There is a lot of occurance with the following registry directory: "Software\Policies\Microsoft\Windows Defender"
It is found under the parent directory of HKLM64.

008CE9E8  043DCA88  L"HKLM64"
...
008CEA08  043DCBC0  L"SOFTWARE\\Policies\\Microsoft\\Windows Defender"

The second breakpoint leads us here:

008CE8F0  043DCFE8  L"HKLM64"
...
008CE910  043DD120  L"SYSTEM\\CurrentControlSet\\Services\\WinDefend"

So taking a look into the registry: SYSTEM\CurrentControlSet\Services\WinDefend
and cross referencing back to x64 dbg: we notice this:

76122F7F | 397D 0C | cmp dword ptr ss:[ebp+C],edi | [ebp+C]:L"Start"

It appears that 0x03 disables windefender, while 0x02 means to enable. A quick google search brings us here: https://answers.microsoft.com/en-us/protect/forum/protect_defender-protect_start-windows_10/how-to-disable-windows-defender-in-windows-10/b834d36e-6da8-42a8-85f6-da9a520f05f2

The next one is also in HKLM:

76122FF0 | 8945 CC                  | mov dword ptr ss:[ebp-34],eax           | [ebp-34]:L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\StartupApproved\\Run"
76122FF3 | 66:8B01                  | mov ax,word ptr ds:[ecx]                | ecx:&L"SecurityHealth"

Seems to be set to 3 or off

Now we will look at RegCreateKey
There seems to be a regisatry opened at

EDX : 043DCD78     L"SOFTWARE\\Microsoft\\Windows Defender\\Real-Time Protection"
EIP : 7591E420     <advapi32.RegCreateKeyExW>

However, there doesnt seem to be anymore functions breakpointed. So lets inspect the directory

We have 2 flags set: DisableRealtimeMonitoring as a REG_DWORD set to 0x01 DpaDisabled as REG_DWORD set to 0x0

Another one opened here:

008CEFF8  043EB4C8  L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\StartupApproved\\Run"

enabling defender

there seems to be a reference with "Policy Manager" using RegEnumKeyExW

It seems to call RegDeleteValueW on security health (see above)

reversing w hooks

We are going to write a simple dll to inject into defender control to dump out the parameters of the functions we are interested in.

Here are the logs:

obtained RegDeleteKeyW from 75A60000
obtained RegDeleteValueW from 75A60000
obtained RegEnumValueW from 75A60000
obtained RegSetValueExW from 75A60000
obtained RegCreateKeyExW from 75A60000
obtained RegConnectRegistryW from 75A60000
obtained RegEnumKeyExW from 75A60000
obtained RegQueryValueExW from 75A60000
obtained RegOpenKeyExW from 75A60000
imports resolved
preparing to hook

Registry Routine to check if defender activated:

[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegQueryValueExW]
lpValueName: DisableRealtimeMonitoring
[RegQueryValueExW]
lpValueName: DisableRealtimeMonitoring
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Exclusions\Paths
[RegQueryValueExW]
lpValueName: C:\Program Files (x86)\DefenderControl\dControl.exe

Routine to disable defender

[RegCreateKeyExW]
lpSubKey: SOFTWARE\Policies\Microsoft\Windows Defender
[RegSetValueExW]
lpValueName: DisableAntiSpyware
[RegCreateKeyExW]
lpSubKey: SOFTWARE\Microsoft\Windows Defender
[RegCreateKeyExW]
lpSubKey: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender
[RegQueryValueExW]
lpValueName: DisableAntiSpyware
[RegQueryValueExW]
lpValueName: DisableAntiSpyware
[RegCreateKeyExW]
lpSubKey: SYSTEM\CurrentControlSet\Services\WinDefend
[RegSetValueExW]
lpValueName: Start
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Run
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Run
[RegQueryValueExW]
lpValueName: SecurityHealth
[RegQueryValueExW]
lpValueName: SecurityHealth
[RegCreateKeyExW]
lpSubKey: SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\StartupApproved\Run
[RegSetValueExW]
lpValueName: SecurityHealth
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Run
[RegEnumValueW]
lpValueName: SecurityHealth
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegQueryValueExW]
lpValueName: DisableRealtimeMonitoring
[RegQueryValueExW]
lpValueName: DisableRealtimeMonitoring
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Exclusions\Paths
[RegQueryValueExW]
lpValueName: C:\Program Files (x86)\DefenderControl\dControl.exe

Routine to enable defender

[RegOpenKeyExW]
lpValueName: SOFTWARE\Policies\Microsoft\Windows Defender
[RegOpenKeyExW]
lpValueName: Policy Manager
[RegOpenKeyExW]
lpValueName: SOFTWARE\Policies\Microsoft\Windows Defender
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender
[RegQueryValueExW]
lpValueName: DisableAntiSpyware
[RegQueryValueExW]
lpValueName: DisableAntiSpyware
[RegOpenKeyExW]
lpValueName: SOFTWARE\Policies\Microsoft\Windows Defender
[RegOpenKeyExW]
lpValueName: SOFTWARE\Policies\Microsoft\Windows Defender
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender
[RegQueryValueExW]
lpValueName: DisableAntiSpyware
[RegQueryValueExW]
lpValueName: DisableAntiSpyware
[RegOpenKeyExW]
lpValueName: SYSTEM\CurrentControlSet\Services\SecLogon
[RegQueryValueExW]
lpValueName: Start
[RegQueryValueExW]
lpValueName: Start
[RegOpenKeyExW]
lpValueName: SOFTWARE\Policies\Microsoft\Windows Defender
[RegOpenKeyExW]
lpValueName: Policy Manager
[RegOpenKeyExW]
lpValueName: SOFTWARE\Policies\Microsoft\Windows Defender
[RegOpenKeyExW]
lpValueName: Policy Manager
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender
[RegQueryValueExW]
lpValueName: DisableAntiSpyware
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegQueryValueExW]
lpValueName: DisableRealtimeMonitoring
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Run
[RegEnumValueW]
lpValueName: SecurityHealth
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Run
[RegQueryValueExW]
lpValueName: SecurityHealth
[RegQueryValueExW]
lpValueName: SecurityHealth
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\StartupApproved\Run
[RegDeleteValueW]
lpValueNameSecurityHealth
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Run
[RegEnumValueW]
lpValueName: SecurityHealth
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Run
[RegQueryValueExW]
lpValueName: WindowsDefender
[RegQueryValueExW]
lpValueName: WindowsDefender
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Run
[RegEnumValueW]
lpValueName: WindowsDefender
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegQueryValueExW]
lpValueName: DisableRealtimeMonitoring
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Exclusions\Paths
[RegQueryValueExW]
lpValueName: C:\Program Files (x86)\DefenderControl\dControl.exe
<also redacted a bunch of stuff from policy manager stuff>

So by analyzing these logs, it seems that we check if defender is enabled by reading these two registries:

SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
DisableRealtimeMonitoring

When it disables the AV it modifies these registries:

[RegCreateKeyExW]
lpSubKey: SOFTWARE\Policies\Microsoft\Windows Defender
[RegSetValueExW]
lpValueName: DisableAntiSpyware
[RegCreateKeyExW]
lpSubKey: SOFTWARE\Microsoft\Windows Defender
[RegCreateKeyExW]
lpSubKey: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegCreateKeyExW]
lpSubKey: SYSTEM\CurrentControlSet\Services\WinDefend
[RegSetValueExW]
lpValueName: Start
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Run
[RegQueryValueExW]
lpValueName: SecurityHealth
[RegCreateKeyExW]
lpSubKey: SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\StartupApproved\Run
[RegSetValueExW]
lpValueName: SecurityHealth
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows\CurrentVersion\Run
[RegEnumValueW]
lpValueName: SecurityHealth
[RegOpenKeyExW]
lpValueName: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
[RegQueryValueExW]
lpValueName: DisableRealtimeMonitoring

Dumping VTable Calls

[Control Table] 0x495b78
[Control Table] 0x493658
[Control Table] 0x4932f8
[Control Table] 0x494e1c
[Control Table] 0x4949e4
[Control Table] 0x4965e0
[Control Table] 0x496088
[Control Table] 0x4951c4
[Control Table] 0x4960d0
[Control Table] 0x49463c
[Control Table] 0x493808
[Control Table] 0x493850
[Control Table] 0x494ed0
[Control Table] 0x49382c
[Control Table] 0x49532c
[Control Table] 0x493874
[Control Table] 0x493898
[Control Table] 0x4931fc
[Control Table] 0x4931b4
[Control Table] 0x495500
[Control Table] 0x495cbc
[Control Table] 0x495ce0
[Control Table] 0x4958cc
[Control Table] 0x494a74
[Control Table] 0x495c08
[Control Table] 0x494cfc
[Control Table] 0x493c40
[Control Table] 0x493e5c
[Control Table] 0x493ea4
[Control Table] 0x493b8c
[Control Table] 0x495b0c
[Control Table] 0x495c2c
[Control Table] 0x493f7c
[Control Table] 0x4930dc
[Control Table] 0x493fe8
[Control Table] 0x494c00
[Control Table] 0x495644
[Control Table] 0x495428
[Control Table] 0x496430
[Control Table] 0x4963e8
[Control Table] 0x4954b8
[Control Table] 0x4945d0
[Control Table] 0x496040
[Control Table] 0x4960ac
[Control Table] 0x494a50
[Control Table] 0x495be4

To enable the AV, we just do the opposite of what we needed to disable the AV.

Upon starting the AV, the program calls CreateProcessW on C:\Windows\System32\SecurityHealthSystray.exe

Windows Tamper Protection

But theres, a catch. In a newer recent windows update - you can no longer disable the defender via registries. Well, our program runs completely in usermode, so there must be another way its making these registry changes - most likely through the powershell command Set-MpPreference if we do some research into changing the registry. So we will need to take a peek into the wmic api it accesses.
Luckily for us, all this stuff is documented. Check out these two links:

• https://docs.microsoft.com/en-us/powershell/module/defender/set-mppreference?view=windowsserver2019-ps
• https://docs.microsoft.com/en-us/windows/win32/wmisdk/wmi-c---application-examples

So, since its kind of difficult to debug the values DefenderControl accesses and this stuff is pretty well documented - we are going to base our work off research.

I first wanted to see how powershell called the command, so i looked through the powershell github since its open sourced and found that the command was in a cmdlet that was not documented in the repository. So after reading up on some powershell commands I dumped the powershell informating using this:

Get-Command Set-MpPreference | fl

If we wanted to read the MSFT_MpPreference class, it is documented here: https://docs.microsoft.com/en-us/previous-versions/windows/desktop/legacy/dn455323(v=vs.85)#requirements
We can access via powershell like so:

Get-WmiObject -ClassName MSFT_MpPreference -Namespace root/microsoft/windows/defender

If we look further we can write to this using the WMI as i suspected, it is documented here: https://docs.microsoft.com/en-us/previous-versions/windows/desktop/defender/windows-defender-wmiv2-apis-portal

We can find the specific wmi com classes if we do the following command:

MpPreference |fl *

We get an output and we are intrested in this:

CimClass                                      : root/Microsoft/Windows/Defender:MSFT_MpPreference
CimInstanceProperties                         : {AllowDatagramProcessingOnWinServer, AllowNetworkProtectionDownLevel,
                                                AllowNetworkProtectionOnWinServer,
                                                AttackSurfaceReductionOnlyExclusions...}
CimSystemProperties                           : Microsoft.Management.Infrastructure.CimSystemProperties

We can find the class here: https://docs.microsoft.com/en-us/dotnet/api/microsoft.management.infrastructure.cimsystemproperties?view=powershellsdk-7.0.0

It is also located in windows binaries in the following path: C:\Program Files (x86)\Reference Assemblies\Microsoft\WMI\v1.0