Adversaries may interact with the Windows Registry to hide configuration information within Registry keys, remove information as part of cleaning up, or as part of other techniques to aid in Persistence and Execution.
Access to specific areas of the Registry depends on account permissions, some requiring administrator-level access. The built-in Windows command-line utility Reg may be used for local or remote Registry modification.  Other tools may also be used, such as a remote access tool, which may contain functionality to interact with the Registry through the Windows API (see examples).
Registry modifications may also include actions to hide keys, such as prepending key names with a null character, which will cause an error and/or be ignored when read via Reg or other utilities using the Win32 API.  Adversaries may abuse these pseudo-hidden keys to conceal payloads/commands used to establish Persistence.  
The Registry of a remote system may be modified to aid in execution of files as part of Lateral Movement. It requires the remote Registry service to be running on the target system.  Often Valid Accounts are required, along with access to the remote system's Windows Admin Shares for RPC communication.
DarkComet adds a Registry value for its installation routine to the Registry Key
|Exaramel for Windows|
Hydraq creates a Registry subkey to register its created service, and can also uninstall itself later by deleting this value. Hydraq's backdoor also enables remote attackers to modify and delete subkeys.
Once Shamoon has access to a network share, it enables the RemoteRegistry service on the target system. It will then connect to the system with RegConnectRegistryW and modify the Registry to disable UAC remote restrictions by setting
TYPEFRAME can install encrypted configuration data under the Registry key
|Restrict Registry Permissions||
Ensure proper permissions are set for Registry hives to prevent users from modifying keys for system components that may lead to privilege escalation.
Modifications to the Registry are normal and occur throughout typical use of the Windows operating system. Consider enabling Registry Auditing on specific keys to produce an alertable event (Event ID 4657) whenever a value is changed (though this may not trigger when values are created with Reghide or other evasive methods).  Changes to Registry entries that load software on Windows startup that do not correlate with known software, patch cycles, etc., are suspicious, as are additions or changes to files within the startup folder. Changes could also include new services and modification of existing binary paths to point to malicious files. If a change to a service-related entry occurs, then it will likely be followed by a local or remote service start or restart to execute the file.
Monitor processes and command-line arguments for actions that could be taken to change or delete information in the Registry. Remote access tools with built-in features may interact directly with the Windows API to gather information. Information may also be acquired through Windows system management tools such as Windows Management Instrumentation and PowerShell, which may require additional logging features to be configured in the operating system to collect necessary information for analysis.
Monitor for processes, command-line arguments, and API calls associated with concealing Registry keys, such as Reghide.  Inspect and cleanup malicious hidden Registry entries using Native Windows API calls and/or tools such as Autoruns  and RegDelNull .
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