Windows Enumeration is a technique commonly implemented in Remote Access Trojans (RATs) and has been present in malware since the early days. While it may not always serve a critical purpose, it remains a popular feature, especially among less sophisticated threat actors or "script kiddies" as a way to observe and interfere with a victim's desktop activity.

The function typically allows the attacker to enumerate all windows on the victim's system. This can include listing window titles, retrieving associated process IDs, and obtaining window handles (HWNDs). The attacker may then use this information to manipulate the user interface by minimizing, maximizing, hiding, showing, or forcibly closing application windows, which can disrupt the victim’s workflow or serve as a form of harassment.

Beyond nuisance behavior, window enumeration can inadvertently expose sensitive information. For example:

• Web browsers often include the title of the currently visited webpage in the window title, potentially leaking browsing habits or visited URLs.
• Messaging and chat applications (e.g., the now-defunct MSN Messenger) sometimes display contact names or recent message snippets in the window title.

Furthermore, acquiring the handle to a specific window can be a stepping stone for more advanced attacks. With access to a window handle, a RAT can:

• Simulate user input (e.g., keystrokes or mouse clicks)
• Take targeted screenshots of specific windows rather than the entire screen
• Inject custom messages or code into the message queue of the application

Featured Windows APIs

• EnumWindows User32.dll
• GetWindowsTextLengthW User32.dll
• GetWindowsText User32.dll