Privilege Escalation

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Tactic Description

Privilege escalation is the result of actions that allow an adversary to obtain a higher level of permissions on a system or network. Certain tools or actions require a higher level of privilege to work and are likely necessary at many points throughout an operation. Adversaries can enter a system with unprivileged access and must take advantage of a system weakness to obtain local administrator or SYSTEM privileges. A user account with administrator-like access can also be used. User accounts with permissions to access specific systems or perform specific functions necessary for adversaries to achieve their objective may also be considered an escalation of privilege.

Techniques

Below is a list of all the Privilege Escalation techniques in enterprise:

NameTacticsTechnical Description
Access Token ManipulationDefense Evasion
Privilege Escalation
Windows uses access tokens to determine the ownership of a running process. A user can manipulate access tokens to make a running process appear as though it belongs to someone other than the user that started the process. When this occurs, the process also takes on the security context associated with the new token. For example, Microsoft promotes the use of access tokens as a security best practice. Administrators should log in as a standard user but run their tools with administrator privileges using the built-in access token manipulation command runas. Microsoft runas

Adversaries may use access tokens to operate under a different user or system security context to perform actions and evade detection. An adversary can use built-in Windows API functions to copy access tokens from existing processes; this is known as token stealing. An adversary must already be in a privileged user context (i.e. administrator) to steal a token. However, adversaries commonly use token stealing to elevate their security context from the administrator level to the SYSTEM level.Pentestlab Token Manipulation

Adversaries can also create spoofed access tokens if they know the credentials of a user. Any standard user can use the runas command, and the Windows API functions, to do this; it does not require access to an administrator account.

Lastly, an adversary can use a spoofed token to authenticate to a remote system as the account for that token if the account has appropriate permissions on the remote system.

Metasploit’s Meterpreter payload allows arbitrary token stealing and uses token stealing to escalate privileges. Metasploit access token The Cobalt Strike beacon payload allows arbitrary token stealing and can also create tokens. Cobalt Strike Access Token
Accessibility FeaturesPersistence
Privilege Escalation
Windows contains accessibility features that may be launched with a key combination before a user has logged in (for example, when the user is on the Windows logon screen). An adversary can modify the way these programs are launched to get a command prompt or backdoor without logging in to the system.

Two common accessibility programs are C:\Windows\System32\sethc.exe, launched when the shift key is pressed five times and C:\Windows\System32\utilman.exe, launched when the Windows + U key combination is pressed. The sethc.exe program is often referred to as "sticky keys", and has been used by adversaries for unauthenticated access through a remote desktop login screen.FireEye Hikit Rootkit

Depending on the version of Windows, an adversary may take advantage of these features in different ways because of code integrity enhancements. In newer versions of Windows, the replaced binary needs to be digitally signed for x64 systems, the binary must reside in %systemdir%\, and it must be protected by Windows File or Resource Protection (WFP/WRP).DEFCON2016 Sticky Keys The debugger method was likely discovered as a potential workaround because it does not require the corresponding accessibility feature binary to be replaced. Examples for both methods:

For simple binary replacement on Windows XP and later as well as and Windows Server 2003/R2 and later, for example, the program (e.g., C:\Windows\System32\utilman.exe) may be replaced with "cmd.exe" (or another program that provides backdoor access). Subsequently, pressing the appropriate key combination at the login screen while sitting at the keyboard or when connected over Remote Desktop Protocol will cause the replaced file to be executed with SYSTEM privileges.Tilbury 2014

For the debugger method on Windows Vista and later as well as Windows Server 2008 and later, for example, a Registry key may be modified that configures "cmd.exe," or another program that provides backdoor access, as a "debugger" for the accessibility program (e.g., "utilman.exe"). After the Registry is modified, pressing the appropriate key combination at the login screen while at the keyboard or when connected with RDP will cause the "debugger" program to be executed with SYSTEM privileges.Tilbury 2014

Other accessibility features exist that may also be leveraged in a similar fashion:DEFCON2016 Sticky Keys

  • On-Screen Keyboard: C:\Windows\System32\osk.exe
  • Magnifier: C:\Windows\System32\Magnify.exe
  • Narrator: C:\Windows\System32\Narrator.exe
  • Display Switcher: C:\Windows\System32\DisplaySwitch.exe
  • App Switcher: C:\Windows\System32\AtBroker.exe
AppInit DLLsPersistence
Privilege Escalation
DLLs that are specified in the AppInit_DLLs value in the Registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Windows are loaded by user32.dll into every process that loads user32.dll. In practice this is nearly every program. This value can be abused to obtain persistence by causing a DLL to be loaded into most processes on the computer.AppInit Registry The AppInit DLL functionality is disabled in Windows 8 and later versions when secure boot is enabled.AppInit Secure Boot
Application ShimmingExecution
Persistence
Privilege Escalation
The Microsoft Windows Application Compatibility Infrastructure/Framework (Application Shim) was created to allow compatibility of programs as Windows updates and changes its code. For example, application shimming feature that allows programs that were created for Windows XP to work with Windows 10. Within the framework, shims are created to act as a buffer between the program (or more specifically, the Import Address Table) and the Windows OS. When a program is executed, the shim cache is referenced to determine if the program requires the use of the shim database (.sdb). If so, the shim database uses API hooking to redirect the code as necessary in order to communicate with the OS. A list of all shims currently installed by the default Windows installer (sdbinst.exe) is kept in:
  • %WINDIR%\AppPatch\sysmain.sdb
  • hklm\software\microsoft\windows nt\currentversion\appcompatflags\installedsdb

Custom databases are stored in:

  • %WINDIR%\AppPatch\custom & %WINDIR%\AppPatch\AppPatch64\Custom
  • hklm\software\microsoft\windows nt\currentversion\appcompatflags\custom
To keep shims secure, Windows designed them to run in user mode so they cannot modify the kernel and you must have administrator privileges to install a shim. However, certain shims can be used to Bypass User Account Control (UAC) (RedirectEXE), inject DLLs into processes (InjectDll), and intercept memory addresses (GetProcAddress). Utilizing these shims, an adversary can perform several malicious acts, such as elevate privileges, install backdoors, disable defenses like Windows Defender, etc.
Bypass User Account ControlDefense Evasion
Privilege Escalation
Windows User Account Control (UAC) allows a program to elevate its privileges to perform a task under administrator-level permissions by prompting the user for confirmation. The impact to the user ranges from denying the operation under high enforcement to allowing the user to perform the action if they are in the local administrators group and click through the prompt or allowing them to enter an administrator password to complete the action.TechNet How UAC Works

If the UAC protection level of a computer is set to anything but the highest level, certain Windows programs are allowed to elevate privileges or execute some elevated COM objects without prompting the user through the UAC notification box.TechNet Inside UACMSDN COM Elevation An example of this is use of rundll32.exe to load a specifically crafted DLL which loads an auto-elevated COM object and performs a file operation in a protected directory which would typically require elevated access. Malicious software may also be injected into a trusted process to gain elevated privileges without prompting a user.Davidson Windows Adversaries can use these techniques to elevate privileges to administrator if the target process is unprotected.

Many methods have been discovered to bypass UAC. The Github readme page for UACMe contains an extensive list of methodsGithub UACMe that have been discovered and implemented within UACMe, but may not be a comprehensive list of bypasses. Additional bypass methods are regularly discovered and some used in the wild, such as:

  • eventvwr.exe can auto-elevate and execute a specified binary or script.enigma0x3 Fileless UAC BypassFortinet Fareit
Another bypass is possible through some Lateral Movement techniques if credentials for an account with administrator privileges are known, since UAC is a single system security mechanism, and the privilege or integrity of a process running on one system will be unknown on lateral systems and default to high integrity.SANS UAC Bypass
DLL InjectionDefense Evasion
Privilege Escalation
DLL injection is used to run code in the context of another process by causing the other process to load and execute code. Running code in the context of another process provides adversaries many benefits, such as access to the process's memory and permissions. It also allows adversaries to mask their actions under a legitimate process. A more sophisticated kind of DLL injection, reflective DLL injection, loads code without calling the normal Windows API calls, potentially bypassing DLL load monitoring. Numerous methods of DLL injection exist on Windows, including modifying the Registry, creating remote threads, Windows hooking APIs, and DLL pre-loading.CodeProject Inject CodeWikipedia DLL Injection
DLL Search Order HijackingDefense Evasion
Persistence
Privilege Escalation
Windows systems use a common method to look for required DLLs to load into a program.Microsoft DLL Search Adversaries may take advantage of the Windows DLL search order and programs that ambiguously specify DLLs to gain privilege escalation and persistence.

Adversaries may perform DLL preloading, also called binary planting attacks,OWASP Binary Planting by placing a malicious DLL with the same name as an ambiguously specified DLL in a location that Windows searches before the legitimate DLL. Often this location is the current working directory of the program. Remote DLL preloading attacks occur when a program sets its current directory to a remote location such as a Web share before loading a DLL.Microsoft 2269637 Adversaries may use this behavior to cause the program to load a malicious DLL.

Adversaries may also directly modify the way a program loads DLLs by replacing an existing DLL or modifying a .manifest or .local redirection file, directory, or junction to cause the program to load a different DLL to maintain persistence or privilege escalation.Microsoft DLL RedirectionMicrosoft ManifestsMandiant Search Order

If a search order-vulnerable program is configured to run at a higher privilege level, then the adversary-controlled DLL that is loaded will also be executed at the higher level. In this case, the technique could be used for privilege escalation from user to administrator or SYSTEM or from administrator to SYSTEM, depending on the program.

Programs that fall victim to path hijacking may appear to behave normally because malicious DLLs may be configured to also load the legitimate DLLs they were meant to replace.
Dylib HijackingPersistence
Privilege Escalation
macOS and OS X use a common method to look for required dynamic libraries (dylib) to load into a program based on search paths. Adversaries can take advantage of ambiguous paths to plant dylibs to gain privilege escalation or persistence.

A common method is to see what dylibs an application uses, then plant a malicious version with the same name higher up in the search path. This typically results in the dylib being in the same folder as the application itselfWriting Bad Malware for OSXMalware Persistence on OS X.

If the program is configured to run at a higher privilege level than the current user, then when the dylib is loaded into the application, the dylib will also run at that elevated level. This can be used by adversaries as a privilege escalation technique.
Exploitation of VulnerabilityCredential Access
Defense Evasion
Lateral Movement
Privilege Escalation
Exploitation of a software vulnerability occurs when an adversary takes advantage of a programming error in a program, service, or within the operating system software or kernel itself to execute adversary-controlled code. Exploiting software vulnerabilities may allow adversaries to run a command or binary on a remote system for lateral movement, escalate a current process to a higher privilege level, or bypass security mechanisms. Exploits may also allow an adversary access to privileged accounts and credentials. One example of this is MS14-068, which can be used to forge Kerberos tickets using domain user permissions.Technet MS14-068ADSecurity Detecting Forged Tickets
File System Permissions WeaknessPersistence
Privilege Escalation
Processes may automatically execute specific binaries as part of their functionality or to perform other actions. If the permissions on the file system directory containing a target binary, or permissions on the binary itself, are improperly set, then the target binary may be overwritten with another binary using user-level permissions and executed by the original process. If the original process and thread are running under a higher permissions level, then the replaced binary will also execute under higher-level permissions, which could include SYSTEM.

Adversaries may use this technique to replace legitimate binaries with malicious ones as a means of executing code at a higher permissions level. If the executing process is set to run at a specific time or during a certain event (e.g., system bootup) then this technique can also be used for persistence.

Services

Manipulation of Windows service binaries is one variation of this technique. Adversaries may replace a legitimate service executable with their own executable to gain persistence and/or privilege escalation to the account context the service is set to execute under (local/domain account, SYSTEM, LocalService, or NetworkService). Once the service is started, either directly by the user (if appropriate access is available) or through some other means, such as a system restart if the service starts on bootup, the replaced executable will run instead of the original service executable.

Executable Installers

Another variation of this technique can be performed by taking advantage of a weakness that is common in executable, self-extracting installers. During the installation process, it is common for installers to use a subdirectory within the %TEMP% directory to unpack binaries such as DLLs, EXEs, or other payloads. When installers create subdirectories and files they often do not set appropriate permissions to restrict write access, which allows for execution of untrusted code placed in the subdirectories or overwriting of binaries used in the installation process. This behavior is related to and may take advantage of DLL Search Order Hijacking. Some installers may also require elevated privileges that will result in privilege escalation when executing adversary controlled code. This behavior is related to Bypass User Account Control. Several examples of this weakness in existing common installers have been reported to software vendors.Mozilla Firefox Installer DLL HijackSeclists Kanthak 7zip Installer
Launch DaemonPersistence
Privilege Escalation
Per Apple’s developer documentation, when macOS and OS X boot up, launchd is run to finish system initialization. This process loads the parameters for each launch-on-demand system-level daemon from the property list (plist) files found in /System/Library/LaunchDaemons and /Library/LaunchDaemonsAppleDocs Launch Agent Daemons. These LaunchDaemons have property list files which point to the executables that will be launchedMethods of Mac Malware Persistence.

Adversaries may install a new launch daemon that can be configured to execute at startup by using launchd or launchctl to load a plist into the appropriate directoriesOSX Malware Detection. The daemon name may be disguised by using a name from a related operating system or benign software WireLurker. Launch Daemons may be created with administrator privileges, but are executed under root privileges, so an adversary may also use a service to escalate privileges from administrator to root.

The plist file permissions must be root:wheel, but the script or program that it points to has no such requirement. So, it is possible for poor configurations to allow an adversary to modify a current Launch Daemon’s executable and gain persistence or Privilege Escalation.
Local Port MonitorPersistence
Privilege Escalation
A port monitor can be set through the AddMonitor API call to set a DLL to be loaded at startup.AddMonitor This DLL can be located in C:\Windows\System32 and will be loaded by the print spooler service, spoolsv.exe, on boot.Bloxham Alternatively, an arbitrary DLL can be loaded if permissions allow writing a fully-qualified pathname for that DLL to HKLM\SYSTEM\CurrentControlSet\Control\Print\Monitors.Bloxham The spoolsv.exe process also runs under SYSTEM level permissions. Adversaries can use this technique to load malicious code at startup that will persist on system reboot and execute as SYSTEM.
New ServicePersistence
Privilege Escalation
When operating systems boot up, they can start programs or applications called services that perform background system functions.TechNet Services A service's configuration information, including the file path to the service's executable, is stored in the Windows Registry. Adversaries may install a new service that can be configured to execute at startup by using utilities to interact with services or by directly modifying the Registry. The service name may be disguised by using a name from a related operating system or benign software with Masquerading. Services may be created with administrator privileges but are executed under SYSTEM privileges, so an adversary may also use a service to escalate privileges from administrator to SYSTEM. Adversaries may also directly start services through Service Execution.
Path InterceptionPersistence
Privilege Escalation
Path interception occurs when an executable is placed in a specific path so that it is executed by an application instead of the intended target. One example of this was the use of a copy of cmd in the current working directory of a vulnerable application that loads a CMD or BAT file with the CreateProcess function.TechNet MS14-019

There are multiple distinct weaknesses or misconfigurations that adversaries may take advantage of when performing path interception: unquoted paths, path environment variable misconfigurations, and search order hijacking. The first vulnerability deals with full program paths, while the second and third occur when program paths are not specified. These techniques can be used for persistence if executables are called on a regular basis, as well as privilege escalation if intercepted executables are started by a higher privileged process.

Unquoted Paths

Service paths (stored in Windows Registry keys)Microsoft Subkey and shortcut paths are vulnerable to path interception if the path has one or more spaces and is not surrounded by quotation marks (e.g., C:\unsafe path with space\program.exe vs. "C:\safe path with space\program.exe").Baggett 2012 An adversary can place an executable in a higher level directory of the path, and Windows will resolve that executable instead of the intended executable. For example, if the path in a shortcut is C:\program files\myapp.exe, an adversary may create a program at C:\program.exe that will be run instead of the intended program.

PATH Environment Variable Misconfiguration

The PATH environment variable contains a list of directories. Certain methods of executing a program (namely using cmd.exe or the command-line) rely solely on the PATH environment variable to determine the locations that are searched for a program when the path for the program is not given. If any directories are listed in the PATH environment variable before the Windows directory, %SystemRoot%\system32 (e.g., C:\Windows\system32), a program may be placed in the preceding directory that is named the same as a Windows program (such as cmd, PowerShell, or Python), which will be executed when that command is executed from a script or command-line.

For example, if C:\example path precedes C:\Windows\system32 is in the PATH environment variable, a program that is named net.exe and placed in C:\example path will be called instead of the Windows system "net" when "net" is executed from the command-line.

Search Order Hijacking

Search order hijacking occurs when an adversary abuses the order in which Windows searches for programs that are not given a path. The search order differs depending on the method that is used to execute the program.Microsoft CreateProcessHill NT ShellMicrosoft WinExec However, it is common for Windows to search in the directory of the initiating program before searching through the Windows system directory. An adversary who finds a program vulnerable to search order hijacking (i.e., a program that does not specify the path to an executable) may take advantage of this vulnerability by creating a program named after the improperly specified program and placing it within the initiating program's directory.

For example, "example.exe" runs "cmd.exe" with the command-line argument net user. An adversary may place a program called "net.exe" within the same directory as example.exe, "net.exe" will be run instead of the Windows system utility net. In addition, if an adversary places a program called "net.com" in the same directory as "net.exe", then cmd.exe /C net user will execute "net.com" instead of "net.exe" due to the order of executable extensions defined under PATHEXT.MSDN Environment Property

Search order hijacking is also a common practice for hijacking DLL loads and is covered in DLL Search Order Hijacking.
Plist ModificationDefense Evasion
Persistence
Privilege Escalation
Property list (plist) files contain all of the information that macOS and OS X uses to configure applications and services. These files are UT-8 encoded and formatted like XML documents via a series of keys surrounded by < >. They detail when programs should execute, file paths to the executables, program arguments, required OS permissions, and many others. plists are located in certain locations depending on their purpose such as /Library/Preferences (which execute with elevated privileges) and ~/Library/Preferences (which execute with a user's privileges). Adversaries can modify these plist files to point to their own code, can use them to execute their code in the context of another user, bypass whitelisting procedures, or even use them as a persistence mechanismSofacy Komplex Trojan.
Scheduled TaskExecution
Persistence
Privilege Escalation
Utilities such as at and schtasks, along with the Windows Task Scheduler, can be used to schedule programs or scripts to be executed at a date and time. The account used to create the task must be in the Administrators group on the local system. A task can also be scheduled on a remote system, provided the proper authentication is met to use RPC and file and printer sharing is turned on.TechNet Task Scheduler Security An adversary may use task scheduling to execute programs at system startup or on a scheduled basis for persistence, to conduct remote Execution as part of Lateral Movement, to gain SYSTEM privileges, or to run a process under the context of a specified account.
Service Registry Permissions WeaknessPersistence
Privilege Escalation
Windows stores local service configuration information in the Registry under HKLM\SYSTEM\CurrentControlSet\Services. The information stored under a service's Registry keys can be manipulated to modify a service's execution parameters through tools such as the service controller, sc.exe, PowerShell, or Reg. Access to Registry keys is controlled through Access Control Lists and permissions.MSDN Registry Key Security If the permissions for users and groups are not properly set and allow access to the Registry keys for a service, then adversaries can change the service binPath/ImagePath to point to a different executable under their control. When the service starts or is restarted, then the adversary-controlled program will execute, allowing the adversary to gain persistence and/or privilege escalation to the account context the service is set to execute under (local/domain account, SYSTEM, LocalService, or NetworkService).
Setuid and SetgidPrivilege EscalationWhen the setuid or setgid bits are set on Linux or macOS for an application, this means that the application will run with the privileges of the owning user or group respectively. Normally an application is run in the current user’s context, regardless of which user or group owns the application. There are instances where programs need to be executed in an elevated context to function properly, but the user running them doesn’t need the elevated privileges. Instead of creating an entry in the sudoers file, which must be done by root, any user can specify the setuid or setgid flag to be set for their own applications. These bits are indicated with an "s" instead of an "x" when viewing a file's attributes via ls -l. The chmod program can set these bits with via bitmasking, chmod 4777 [file] or via shorthand naming, chmod u+s [file]. An adversary can take advantage of this to either do a shell escape or exploit a vulnerability in an application with the setsuid or setgid bits to get code running in a different user’s context.
Startup ItemsPersistence
Privilege Escalation
Per Apple’s documentation, startup items execute during the final phase of the boot process and contain shell scripts or other executable files along with configuration information used by the system to determine the execution order for all startup itemsStartup Items. This is technically a deprecated version (superseded by Launch Daemons), and thus the appropriate folder, /Library/StartupItems isn’t guaranteed to exist on the system by default, but does appear to exist by default on macOS Sierra. A startup item is a directory whose executable and configuration property list (plist), StartupParameters.plist, reside in the top-level directory. An adversary can create the appropriate folders/files in the StartupItems directory to register their own persistence mechanismMethods of Mac Malware Persistence. Additionally, since StartupItems run during the bootup phase of macOS, they will run as root. If an adversary is able to modify an existing Startup Item, then they will be able to Privilege Escalate as well.
SudoPrivilege EscalationThe sudoers file, /etc/sudoers, describes which users can run which commands and from which terminals. This also describes which commands users can run as other users or groups. This provides the idea of least privilege such that users are running in their lowest possible permissions for most of the time and only elevate to other users or permissions as needed, typically by prompting for a password. However, the sudoers file can also specify when to not prompt users for passwords with a line like user1 ALL=(ALL) NOPASSWD: ALLOSX.Dok Malware. Adversaries can take advantage of these configurations to execute commands as other users or spawn processes with higher privileges. You must have elevated privileges to edit this file though.
Valid AccountsDefense Evasion
Persistence
Privilege Escalation
Adversaries may steal the credentials of a specific user or service account using Credential Access techniques. Compromised credentials may be used to bypass access controls placed on various resources on hosts and within the network and may even be used for persistent access to remote systems. Compromised credentials may also grant an adversary increased privilege to specific systems or access to restricted areas of the network. Adversaries may choose not to use malware or tools in conjunction with the legitimate access those credentials provide to make it harder to detect their presence.

Adversaries may also create accounts, sometimes using pre-defined account names and passwords, as a means for persistence through backup access in case other means are unsuccessful.

The overlap of credentials and permissions across a network of systems is of concern because the adversary may be able to pivot across accounts and systems to reach a high level of access (i.e., domain or enterprise administrator) to bypass access controls set within the enterprise.TechNet Credential Theft
Web ShellPersistence
Privilege Escalation
A Web shell is a Web script that is placed on an openly accessible Web server to allow an adversary to use the Web server as a gateway into a network. A Web shell may provide a set of functions to execute or a command-line interface on the system that hosts the Web server. In addition to a server-side script, a Web shell may have a client interface program that is used to talk to the Web server (see, for example, China Chopper Web shell client).Lee 2013 Web shells may serve as Redundant Access or as a persistence mechanism in case an adversary's primary access methods are detected and removed.