the result of actions that allows an adversary to obtain a higher level of permissions on a system or network. We will look at different methods of local privilege escalation in Windows environment and how to detect them via logs.
describes the security context of a process or thread. It is created during logon and never changes* after creation. Token contains: • User SID • Group SIDs / Restricted group SIDs • Integrity level (Mandatory label) • Logon Session SID • Token type (primary or impersonation) • Impersonation level • User privileges list • Other
S-1-16-0 Low Everyone. Used by Protected Mode of Internet Explorer S-1-16-4096 Medium Used by normal applications being launched while UAC is enabled S-1-16-8192 High Privileged users (if UAC enabled) or all authenticated users (if UAC disabled) S-1-16-12288 System LocalSystem. NetworkService, LocalService S-1-16-16384 Default mandatory policy for all objects: No-Write-Up Default mandatory policy for processes: No-Write-Up + No-Read-Up Default implicit integrity level for files – Medium
Control Is access granted? Subject Object Security Descriptor Owner SID Group SID DACL SACL (obj IL is here) Access Token User SID Groups SIDs Privileges Integrity Level Access Denied Access Denied YES YES NO NO Is access granted? Influence on Bypass, using special privileges (Debug, Restore, Backup, Take Ownership)
files may be left in the system. These answer files can contain credentials of the privileged local accounts (e.g. Administrator): • C:\sysprep\sysprep.xml • C:\sysprep\sysprep.inf • C:\sysprep.inf • C:\unattend.xml • C:\Windows\Panther\Unattend.xml • C:\Windows\Panther\Unattend\Unat tend.xml sysprep.xml Base64 “encryption” Unattended.xml Base64 “encryption” sysprep.inf
domain admins to create and deploy across the domain local users and local administrators accounts. In case of usage this function policy preference files are created. These files are located in the SYSVOL shared directory and any authenticated user in the domain has read access to these files since it is needed in order to obtain group policy updates. Policy preference files contain encrypted passwords… But encryption key is hardcoded and published by Microsoft Policy preference files are located: • C:\ProgramData\Microsoft\Group Policy\History\????\Machine\Preferences\Groups\Groups.xml • \\????\SYSVOL\\Policies\????\Machine\Preferences\Groups\Groups.xml Also several other policy preference files can be useful: • Services\Services.xml • ScheduledTasks\ScheduledTasks.xml • Printers\Printers.xml • Drives\Drives.xml • DataSources\DataSources.xml
credentials and passwords that have been stored for use by other programs or services. For example, these credentials can be used for automatic logon. The idea behind the Windows Auto Login is that a user, specified in DefaultUserName can logon at a computer without having to type their password.
HKLM\SYSTEM\CurrentControlSet\Services. Adversaries can change the service ImagePath, FailureCommand or ServiceDll to point to a different executable under their control, if the permissions for users and groups are not properly set and allow access to the Registry keys for a service. Service registry permissions weakness 1. Find writeable registry keys for services, using Accesschk 2. Change ImagePath 3. Restart Service
to modify service configuration in registry: event_id:1 AND event_data.IntegrityLevel:Medium AND ((event_data.CommandLine:*reg* AND event_data.CommandLine:*add*) OR (event_data.CommandLine:*powershell* AND event_data.CommandLine:("*set- itemproperty*" "* sp *" "*new-itemproperty*") )) AND event_data.CommandLine:(*ControlSet* AND *Services*) AND event_data.CommandLine:(*ImagePath* *FailureCommand* *ServiceDll*) Service registry permissions weakness. Let’s hunt it! Medium IL shows us that user is non-privileged
event_data.TargetObject:("\\ImagePath" "\\FailureCommand" "\\ServiceDll") Service registry permissions weakness. Let’s hunt it! Search for changing Services registry keys by non-privileged users: Save to memcached Get from memcached
started processes for further enrichment of other events: • Integrity Level • User • Command line • Parent Image Building information block for caching: Saving previously built information block in cache (key is concatenation of ProcessGuid and computer_name): Cache information about started processes
any object it has DACL. Sometimes it is possible to discover services that run with SYSTEM privileges and don’t have appropriate permissions. Adversaries can use it to elevate privileges by changing the service ImagePath, FailureCommand or ServiceDll to point to a different executable under their control. It can be done via SCM API or using sc.exe utility. 1. Discover service with weak permissions, using Accesschk 2. Change service binPath 3. Restart service
of sc utility by non-privileged users to change service configuration. Medium IL shows us that user is non-privileged Usage of sc to change service binPath Usage of sc to restart service
service binPath or Failure command: source_name:"Microsoft-Windows-Sysmon" AND event_id:1 AND event_data.IntegrityLevel:Medium AND event_data.Image:"\\sc.exe" AND ((event_data.CommandLine:*config* AND event_data.CommandLine:*binPath*) OR (event_data.CommandLine:*failure* AND event_data.CommandLine:*command*)) Service permissions weakness. Let’s hunt it! Medium IL shows us that user is non-privileged
find the location of its executable. In case when executable path is enclosed in quotes Windows has no question about where to find it. But if the executable path contains spaces and isn’t surrounded by quotes OS will try to find file and execute it inside every folder of the path until reach the executable. In this case, the part between the backslash and the space will be treated as the file name, and the remaining part - as command line arguments. Unquoted service path Path with spaces, isn’t surrounded by quotes Finding of service executable
beginning of command line in the quotes doesn’t end with extension and the same as image path without extension. Also there should be cutted part of a file path in the right side of the command line (after the part in quotes): {"bool":{"must":[{"query_string":{"query":" event_id:1 AND event_data.ParentImage:\"*\\\\services.exe\" AND event_data.Image.keyword:*exe AND event_data.CommandLine.keyword:/.*\\\\[\\\\a-zA-Z]+\\\"( | ).+/ AND -event_data.CommandLine:(*svchost* *msiexec* *schtasks* *rundll32*) "}},{"script":{"script":" if (!doc[\"event_data.CommandLine.keyword\"].empty && !doc[\"event_data.Image.keyword\"].empty) { String file_path_stripped = doc[\"event_data.Image.keyword\"].value.toLowerCase().replace(\".exe\",\"\"); String[] filecmdline_parts = /\"\\s/.split(doc[\"event_data.CommandLine.keyword\"].value.toLowerCase()); if (filecmdline_parts.length >= 2 && filecmdline_parts[1].contains(\"\\\\\")) { if (filecmdline_parts[0].substring(1) == file_path_stripped) { return true; } } return false; } "}}]}} Unquoted service path. Let’s hunt it!
the folder of where the binary of the service is located then it is possible to just replace the binary with the a custom payload and then restart the service in order to escalate privileges. Modifiable service binary 1. Find service with writable binary 2. Replace binary and restart service
as a service with the System rights (3) Modifiable service binary. Let’s hunt it! 1 Replacing service binary using xcopy Medium IL shows us that process isn’t privileged 2 3 Modified by non-privileged user file is launched as service under SYSTEM
non-privileged processes: source_name:"Microsoft-Windows-Sysmon" AND event_id:11 AND event_data.IntegrityLevel:Medium AND (event_data.TargetFilename:("\\Program Files\\" "\\Program Files (x86)\\") OR event_data.TargetFilename.keyword:/.\:\\[W|w][I|i][N|n][D|d][O|o][W|w][S|s]\\.*/) AND - event_data.TargetFilename:(*temp*) Modifiable service binary. Let’s hunt it! Get from memcached
that was dropped by non-privileged user: source_name:"Microsoft-Windows-Sysmon" AND event_id:1 AND event_data.ParentImage:"\\services.exe" AND event_data.User:"NT AUTHORITY\\SYSTEM" AND event_data.ImageModifierIntegrityLevel:Medium Modifiable service binary. Let’s hunt it! Key for caching information about dropped file Key for getting information about dropped file from cache
filter it is possible to cache information about created files for further enrichments of other events: Example of enrichment with information about last file modifier
it! Events, related to usage of AccessChk utility to check rights on different objects. Finding writeable registry keys Metadata shows us, that it is renamed AccessChk Finding services, which we can control Metadata shows us, that it is renamed AccessChk
regular user to install a Microsoft Windows Installer Package (MSI) with system privileges. This can be discovered in environments where a standard user wants to install an application which requires system privileges and the administrator would like to avoid to give temporary local administrator access to a user. Always Install Elevated
if non privileged user runs MSI (1), Windows Installer service will try to install it with privileges of the current user (2) Always Install Elevated. Let’s hunt it! 1 2
non privileged user (1) –> Windows Installer service try to install MSI packages with SYSTEM privileges (2): source_name:"Microsoft-Windows-Sysmon" AND event_id:1 AND ( (event_data.Image:("\\Windows\\Installer\\" AND *msi* AND *tmp) AND event_data.User:"NT AUTHORITY\\SYSTEM") OR (event_data.Image:"\\msiexec.exe" AND -event_data.User:"NT AUTHORITY\\SYSTEM" AND -event_data.IntegrityLevel:System) ) Always Install Elevated. Let’s hunt it! 1 2
AND *tmp) source_name:"Microsoft-Windows-Sysmon" AND event_id:1 AND event_data.ParentImage:("\\cmd.exe" "\\powershell.exe") AND event_data.ParentOfParent:("\\Windows\\Installer\\" AND *msi* AND *tmp) Search for spawning of cmd or Powershell by MSI package: Always Install Elevated. Let’s hunt it! Search for spawning of processes from cmd/Powershell, spawned from MSI package:
drivers vulnerabilities can allow an attacker to execute arbitrary code in the kernel mode. The goal of kernel or driver exploitation is often to somehow gain higher privileges (in the most cases SYSTEM). Possible kernel shellcodes, that can be used for LPE: • Token stealing (replacing token of some process with SYSTEM token); • Nulling out ACLs (null DACL means that everybody can access an object); • Changing objects’ ACLs (gives full access to arbitrary object, e.g. to the process with SYSTEM privileges, disable auditing); • Changing tokens (new groups, new “super” privileges, increasing integrity level, changing user SID);
works: • Enumerate EPROCESS structures in kernel memory; • Find the EPROCESS address of the privileged (SYSTEM) process; • Find the EPROCESS address of the current process; • Read ACCESS TOKEN from the privileged process; • Replace ACCESS TOKEN of the current process with ACCESS TOKEN of the privileged process. winlogon.exe Process System cmd.exe Process User System
parents with non- SYSTEM privileges and Medium integrity level: source_name:"Microsoft-Windows-Sysmon" AND event_id:1 AND event_data.ParentIntegrityLevel:Medium AND (event_data.IntegrityLevel:System AND event_data.User:"NT AUTHORITY\\SYSTEM") Windows Kernel and 3rd-party drivers exploits. Token stealing Let’s hunt it! Save to memcached Get from memcached
Performing token swapping to SYSTEM via installed driver 3. Spawning cmd under SYSTEM acciunt 4. Checking current rights Token before swapping Token after swapping Token of spawned cmd
level Token swapping, using Mimikatz driver. Let’s hunt it! Parent process started under account with high IL Child process started under SYSTEM account
High integrity level source_name:"Microsoft-Windows-Sysmon" AND event_id:1 AND event_data.ParentIntegrityLevel:High AND (event_data.IntegrityLevel:System AND event_data.User:"NT AUTHORITY\\SYSTEM") Save to memcached Get from memcached Token swapping, using Mimikatz driver. Let’s hunt it!
SeDebugPrivilege A user with this privilege can open any process on the system without regard to the security descriptor present on the process SeImpersonatePrivilege These privileges can be used to act behalf of another user via impersonation mechanism, It can be used to impersonate thread or to spawn process using an elevated token SeAssignPrimaryPrivilege SeTakeOwnershipPrivilege This privilege allows a holder to take ownership any securable object (even process) SeRestorePrivilege A user assigned this privilege can replace any file on the system with her own or change any registry key SeBackupPrivilege A user assigned this privilege can read any file on the system or any registry key SeLoadDriver A malicious user could use this privilege to execute arbitrary code in the kernel SeCreateTokenPrivilege This privilege can be used to generate tokens that represent arbitrary user accounts with arbitrary group membership and privileges assignment SeTcbPrivilege A malicious user can use this privilege to create new logon session that includes the SIDs of more privileged groups or users in the resulting token
process or thread, regardless of the process’s or thread’s security descriptor (except for protected processes). In case of non-administrative account this privilege can be obtained via kernel exploitation or insecure configuration (direct granting SeDebugPrivilege to non-administrative accounts). How it can be used in the context of privilege escalation: • Reading memory of any process ; • Writing to the memory of any process; • Spawning process with arbitrary parent.
event_data.TargetIntegrityLevel:System Abusing debug privilege. Code injection. Let’s hunt it! Search for injections into the processes with SYSTEM privileges by processes with Medium or High integrity levels: Save to memcached Get from memcached Source process creation event Target process creation event Get from memcached Save to memcached
Abusing debug privilege. Code injection. Let’s hunt it! Search for loading by process with SYSTEM rights of DLL, that was dropped by process with Medium IL: Get from memcached Get from memcached Save to memcached
newly spawned process via the PROC_THREAD_ATTRIBUTE_PARENT_PROCESS attribute. This facility is used by UAC when elevated processes are launched by AppInfo service to look like being launched from non-elevated process that would have been the parent, had there been no elevation. Abusing debug privilege. Create process with arbitrary parent
System 2. Process handle 1. OpenProcess 3. CreateProcess Abusing debug privilege. Create process with arbitrary parent How it works 4. Inherit winlogon.exe process token
"\\spoolsv.exe" "\\searchindexer.exe") AND event_data.Image:("\\cmd.exe" "\\powershell.exe") AND event_data.User:"NT AUTHORITY\\SYSTEM“ AND -event_data.CommandLine:(*route* *ADD*) Abusing debug privilege. Create process with arbitrary parent Let’s hunt it! Search for spawning of unusual child processes by different system processes:
User A Primary token Thread 2 User B Impersonation token Thread 3 User C Impersonation token Impersonation is the ability of a thread to execute in a security context that is different from the context of the process that owns the thread. Using impersonation process can act behalf of other user. The server thread uses an access token representing the client's credentials to obtain access to the objects to which the client has access. Related privileges: • SeImpersonatePrivilege • SeAssignPrimaryPrivilege
Influence on process 2. Connection 3. ImpersonateSecurityContext or ImpersonateNamedPipeClient or DdeImpersonateClient or RpcImpersonateCliet System Primary token Process Child.exe 5. CreateProcessWithToken or CreateProcessAsUser User A Primary token Process Parent.exe Impersonation privilege Abusing impersonation. Tricking privileged process connect to us Endpoint Most actions by the thread are done in the security context of the thread's impersonation. But if an impersonating thread calls the CreateProcess function, the new process inherits the primary token of the process.
(good for offenders ) – currently ANY user can obtain impersonation SYSTEM token by tricking the SYSTEM account into performing authentication to some TCP listener user control! Good news for defenders (bad for offenders) – to use obtained token SeImpersonatePrivilege or SeAssignPrimaryPrivilege is required (to call the ImpersonateSecurityContext function)…
technique 1. Checking current privileges (NETWOR SERVICE) 2. Downloading JucyPotato tool 3. Downloading binary to run with elevated privileges 4. Launching JucyPotato tool 5. Using obtained SYSTEM token to start downloaded binary via CreateProcessWithTokenW API 6. Pwned!
"NT AUTHORITY\\LOCAL SERVICE") AND - event_data.CommandLine:(*rundll32* AND *DavSetCookie*) Abusing impersonation. Service account –> SYSTEM Let’s hunt it! Search for spawning SYSTEM processes by processes, started with Network or Local service account: Get from memcached Save to memcached
getsystem (technique 1 – fileless) Meterpreter getsystem How it works: 1. Creates a named pipe; 2. Creates and starts service, that spawn a cmd.exe under SYSTEM which then connects to created named pipe; 3. After cmd had connected to the pipe, impersonates SYSTEM security context, using ImpersonateNamedPipeClient function.
file dropping) How it works: 1. Creates a named pipe; 2. Drops special DLL with code to connect to named pipe; 3. Creates and stars service, that spawn a rundll32.exe under SYSTEM which then executes code from DLL; 4. Code from DLL connects to the created named pipe; 5. After cmd had connected to the pipe, impersonates SYSTEM security context, using ImpersonateNamedPipeClient function.
*" AND event_data.CommandLine:*pipe* AND event_data.CommandLine.keyword:/.*\\\\.\\..*/) OR (event_data.CommandLine:*rundll* AND event_data.CommandLine.keyword:/.*\.dll,a \/p:.*/)) Abusing impersonation. Named pipe impersonation Meterpreter/Cobalt Strike getsystem. Let’s hunt it! Search for services installation events, where Image Path and command line point to the Meterpreter getsystem command execution (redirection cmd output to the named pipe, specific rundll32 command line):
or DuplicateTokenEx 2. TokenHandle 3.1. SetThreadToken or ImpersonateLoggedOnUser User A Primary token Process Parent.exe Impersonation Debug privileges Abusing impersonation + debug privileges. Steal token of other process via DuplicateToken(Ex) In this case also if an impersonating thread calls the CreateProcess function, the new process inherits the primary token of the process rather than the impersonation token of the calling thread. System Primary token Process Child.exe 3.2. CreateProcessWithToken or CreateProcessAsUser
High integrity level: event_id:1 AND source_name:"Microsoft-Windows-Sysmon" AND event_data.IntegrityLevel:System AND event_data.User:"NT AUTHORITY\\SYSTEM" AND event_data.ParentIntegrityLevel:(Medium High) Abusing impersonation + debug privileges. Tokenvator Let’s hunt it!
from parent process (excluding parent processes for which such activity is legitimate – runas tool for example): {"bool":{"must":[{"query_string":{"query":" event_id:1 AND event_data.ParentIntegrityLevel:(High Medium Low) AND -event_data.Image:\"\\runas.exe\" AND -(event_data.Image:\"rundll32.exe\" AND event_data.CommandLine:*RunAsNewUser_RunDLL*) "}},{"script":{"script":" doc[\"event_data.User.keyword\"] != doc[\"event_data.ParentUser.keyword\"] "}}]}} Generic detector of token swapping Enrichment using logstash memcached filter plugin
event_id:1 AND event_data.Image:"\\whoami.exe" AND event_data.IntegrityLevel:System AND event_data.User:"NT AUTHORITY\\SYSTEM" Generic detector of privilege escalation to SYSTEM
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