Neither Microsoft nor any other browser maker sponsored the report, Moy said. Each browser maker is invited to participate, free of charge, in setting up its browser properly for the test.

The NSS test results confirm claims made by Microsoft about the effectiveness of the blocking features introduced in IE9. Those claims were initially challenged by one security researcher. "Because IE9's unable to block exploits of such software as Adobe Reader and Flash, Apple's iTunes or Oracle 's Java, Microsoft's data doesn't show the real picture," .

NSS tests have been a source of controversy in the past. Its report on firewalls in April had several makers of those products protesting the test results that found their to TCP Split Handshake attacks.

NSS performs this test periodically. Since the last test in the third quarter of 2010, IE9, Chrome, and Opera have improved, while Firefox and Safari did more poorly.

NSS explained that social engineering malware remains the most common security threat facing Internet users today, claiming one third of Internet users as victims. These attacks pose a significant risk to individuals and organizations by threatening to compromise, damage or acquire sensitive personal and corporate information.