Disclosed is a portable security device and method for detection and treatment of computer malware. An example method includes performing a malware detection experiment by the security device on the computer by simulating a connection to the computer of a simulated data storage device containing a predefined set of data. The method further includes determining if there are any modifications in the set of data contained in the simulated data storage device after termination of the malware detection experiment. The method further includes, based on whether there are any modifications in the set of data, determining whether to perform one or more subsequent malware detection experiments by the security device on the computer. In one example aspect, each of the one or more subsequent malware detection experiments are configured to simulate a different connection to the computer of a different simulated data storage device containing the predefined set of data.