Most of todays tools for fingerprinting are focusing on server-side services. Well-known and widely-accepted implementations of such utilities are available for http web services, smtp mail server, ftp servers and even telnet daemons. Of course, many attack scenarios are focusing on server-side attacks. Client-based attacks, especially targeting web clients, are becoming more and more popular. Browser-targeted attacks, drive-by pharming and web-based phishing provide a broad aspect of threats during surfing in the world wide web. Attacker might initialize and optimize their attacks by fingerprinting the target application to find the best possible way to compromise the client.