Adversaries can use methods of capturing user input for obtaining credentials for Valid Accounts and information Collection that include keylogging and user input field interception.
Keylogging is the most prevalent type of input capture, with many different ways of intercepting keystrokes,  but other methods exist to target information for specific purposes, such as performing a UAC prompt or wrapping the Windows default credential provider. 
Keylogging is likely to be used to acquire credentials for new access opportunities when Credential Dumping efforts are not effective, and may require an adversary to remain passive on a system for a period of time before an opportunity arises.
Adversaries may also install code on externally facing portals, such as a VPN login page, to capture and transmit credentials of users who attempt to log into the service. This variation on input capture may be conducted post-compromise using legitimate administrative access as a backup measure to maintain network access through External Remote Services and Valid Accounts or as part of the initial compromise by exploitation of the externally facing web service. 
XAgentOSX contains keylogging functionality that will monitor for active application windows and write them to the log, it can handle special characters, and it will buffer by default 50 characters before sending them out over the C2 infrastructure.
Identify and block potentially malicious software that may be used to acquire credentials or information from the user by using whitelisting  tools, like AppLocker,   or Software Restriction Policies  where appropriate. 
In cases where this behavior is difficult to detect or mitigate, efforts can be made to lessen some of the impact that might result from an adversary acquiring credential information. It is also good practice to follow mitigation recommendations for adversary use of Valid Accounts.
Keyloggers may take many forms, possibly involving modification to the Registry and installation of a driver, setting a hook, or polling to intercept keystrokes. Commonly used API calls include SetWindowsHook, GetKeyState, and GetAsyncKeyState.  Monitor the Registry and file system for such changes and detect driver installs, as well as looking for common keylogging API calls. API calls alone are not an indicator of keylogging, but may provide behavioral data that is useful when combined with other information such as new files written to disk and unusual processes.
Monitor the Registry for the addition of a Custom Credential Provider.  Detection of compromised Valid Accounts in use by adversaries may help to catch the result of user input interception if new techniques are used.
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