Registry Run Keys / Startup Folder
Adversaries may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key. Adding an entry to the "run keys" in the Registry or startup folder will cause the program referenced to be executed when a user logs in. (Citation: Microsoft Run Key) These programs will be executed under the context of the user and will have the account's associated permissions level.
Placing a program within a startup folder will cause that program to execute when a user logs in. There is a startup folder location for individual user accounts as well as a system-wide startup folder that will be checked regardless of which user account logs in.
The startup folder path for the current user is:
* C:\Users\[Username]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup
The startup folder path for all users is:
* C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp
The following run keys are created by default on Windows systems:
* HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
* HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
* HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
* HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce
The HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnceEx
is also available but is not created by default on Windows Vista and newer. Registry run key entries can reference programs directly or list them as a dependency. (Citation: Microsoft RunOnceEx APR 2018) For example, it is possible to load a DLL at logon using a "Depend" key with RunOnceEx: reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx\0001\Depend /v 1 /d "C:\temp\evil[.]dll"
(Citation: Oddvar Moe RunOnceEx Mar 2018)
The following Registry keys can be used to set startup folder items for persistence:
* HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
* HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
* HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
* HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
The following Registry keys can control automatic startup of services during boot:
* HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce
* HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce
* HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices
* HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServices
Using policy settings to specify startup programs creates corresponding values in either of two Registry keys:
* HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
* HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
The Winlogon key controls actions that occur when a user logs on to a computer running Windows 7. Most of these actions are under the control of the operating system, but you can also add custom actions here. The HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Userinit
and HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell
subkeys can automatically launch programs.
Programs listed in the load value of the registry key HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
run when any user logs on.
By default, the multistring BootExecute value of the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager
is set to autocheck autochk *. This value causes Windows, at startup, to check the file-system integrity of the hard disks if the system has been shut down abnormally. Adversaries can add other programs or processes to this registry value which will automatically launch at boot.
Adversaries can use these configuration locations to execute malware, such as remote access tools, to maintain persistence through system reboots. Adversaries may also use Masquerading to make the Registry entries look as if they are associated with legitimate programs.
Mitigations |
|
Mitigation | Description |
---|---|
Registry Run Keys / Startup Folder Mitigation |
Identify and block potentially malicious software that may be executed through run key or startup folder persistence using whitelisting (Citation: Beechey 2010) tools like AppLocker (Citation: Windows Commands JPCERT) (Citation: NSA MS AppLocker) or Software Restriction Policies (Citation: Corio 2008) where appropriate. (Citation: TechNet Applocker vs SRP) |
Detection
Monitor Registry for changes to run keys that do not correlate with known software, patch cycles, etc. Monitor the start folder for additions or changes. Tools such as Sysinternals Autoruns may also be used to detect system changes that could be attempts at persistence, including listing the run keys' Registry locations and startup folders. (Citation: TechNet Autoruns) Suspicious program execution as startup programs may show up as outlier processes that have not been seen before when compared against historical data. Changes to these locations typically happen under normal conditions when legitimate software is installed. To increase confidence of malicious activity, data and events should not be viewed in isolation, but as part of a chain of behavior that could lead to other activities, such as network connections made for Command and Control, learning details about the environment through Discovery, and Lateral Movement.
References
- Russinovich, M. (2016, January 4). Autoruns for Windows v13.51. Retrieved June 6, 2016.
- Moe, O. (2018, March 21). Persistence using RunOnceEx - Hidden from Autoruns.exe. Retrieved June 29, 2018.
- Microsoft. (2018, August 20). Description of the RunOnceEx Registry Key. Retrieved June 29, 2018.
- Microsoft. (n.d.). Run and RunOnce Registry Keys. Retrieved November 12, 2014.
Связанные риски
Каталоги
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