It took developers of the Immunity security testing tool two hours to their exploit, after Microsoft released a patch for the issue Thursday morning. Software developed by Immunity is made available only to paying customers, which means that not everyone has access to the new attack, but security experts expect that some version of the code will begin circulating in public very soon.

Microsoft took the unusual step of rushing out an emergency patch for the flaw Thursday, two weeks after noticing a small number of targeted attacks that exploited the bug.

The vulnerability was not publicly known before Thursday; however, by issuing its patch, Microsoft has given hackers and security researchers enough information to develop their own attack code.

The flaw lies in the Windows Server service, used to connect different network resources such as file and print servers over a network. By sending malicious messages to a Windows machine that uses Windows Server, an attacker could take control of the computer, Microsoft said.

Apparently, it doesn't take much effort to write this type of attack code.