Archiving Your IIS Log Files
It is recommended that you periodically move your log files from your Web servers to a more secure location. When you move these files, you must do it in a secure way. One way to achieve security is to use separate network segments that run directly from your staging environment to your production environment. Separate network segments are a good way to update content, and to move log files to secure servers. Another way to safely move log files is through Secure Sockets Layer (SSL) over HTTP or File Transfer Protocol (FTP).
By default, IIS log files are stored in the <drive>:\WINNT\system32\LogFiles\W3SVC# folder on the computer running IIS, where <drive> is the drive partition where Windows is installed and # is the number of the site.
By default, Pipeline logging files are stored in the \Pipeline\Logfiles folder in the Web application.