Keyloggers are serious threats for computer users both private and commercial. If an attacker is capable of installing this malware on the victim’s machine then he or she is able to monitor keystrokes of a user. This keylog contains login information. As a consequence, protection and detection techniques against keyloggers become increasingly better. This article presents the method of Mouse Underlaying for creating a new kind of software based keyloggers. This method is implemented in Java for testing countermeasures concerning keylogger protection, virtual keyboard, signatures and behavior detection by anti-virus programs. Products of various manufacturers are used for demonstration purposes. All of them failed without an exception. In addition, the reasons why these products failed are analyzed, and moreover, measures against Mouse Underlaying are developed based on the demonstration results.