Microsoft released five critical bulletins to address vulnerabilities in Windows and protect customers from two types of threats in September: 1. Browser based attacks where websites hosting malicious code attempt to compromise visitors. This includes MS09-045, MS09-046 and MS09-047. 2. Network based scenarios where attackers attempt Remote Code Execution (RCE) or Denial-of-Service (DoS) type attacks. This includes MS09-048 and MS09-049.

Full Article: MSRC blog