Detect Hidden Windows with this Detection Rule

Adversaries may implement hidden windows to conceal malicious activity from the plain sight of users. In some cases, windows that would typically be displayed when an application carries out an operation can be hidden. This may be utilized by system administrators to avoid disrupting user work environments when carrying out administrative tasks. Adversaries may abuse operating system functionality to hide otherwise visible windows from users so as not to alert the user to adversary activity on the system.

ID: T1143

Tactic: Defense Evasion

Platform: macOS, Windows

Permissions Required: User

Data Sources: Windows event logs, PowerShell logs, Process command-line parameters, Process monitoring, File monitoring

Procedure Examples

APT19: APT19 used -W Hidden to conceal PowerShell windows by setting the WindowStyle parameter to hidden

APT28: APT28 has used the WindowStyle parameter to conceal PowerShell windows

Mitigation

Execution Prevention: Limit or restrict program execution using anti-virus software. On MacOS, whitelist programs are allowed to have the plist tag. All other programs should be considered suspicious.

Detection

Monitor processes and command-line arguments for actions indicative of hidden windows. In Windows, enable and configure event logging and PowerShell logging to check for the hidden window style. In MacOS, plist files are ASCII text files with a specific format, so they’re relatively easy to parse. File monitoring can check for the apple.awt.UIElement or any other suspicious plist tag in plist files and flag them.

Windows

There are a variety of features in scripting languages in Windows, such as PowerShell, Jscript, and VBScript to make windows hidden. One example of this is powershell.exe -WindowStyle Hidden.

Mac

The configurations for how applications run on macOS are listed in the property list (plist) files. One of the tags in these files can be apple.awt.UIElement, which allows for Java applications to prevent the application’s icon from appearing in the Dock. A common use for this is when applications run in the system tray, but don’t also want to show up in the Dock. However, adversaries can abuse this feature and hide their running window.

The resource of Hidden Windows with this free Splunk Detection Rule:

https://attack.mitre.org/