The out-of-band update comes exactly 21 days after Microsoft said it was aware of targeted attacks against Windows users running its flagship browser. The vulnerability in question only affects Internet Explorer 6 Service Pack 1 on Microsoft Windows 2000 Service Pack 4, and IE Explorer 6 and Internet Explorer 7. An Israeli hacker was able to piece together clues to reproduce the vulnerability and release exploit code into the Metasploit hacking tool. The earliest attacks against this vulnerability includeed the use of a backdoor that allows complete access to a vulnerable machine.
Source: https://threatpost.com/microsoft-readies-emergency-ie-patch-thwart-attacks-032910/73754/