I guess there is a need for this offering around the world to accommodate those computers that are not directly connected to the internet and therefore unable to get the monthly Patch Tuesday updates easily.

So to help with that Microsoft always releases an ISO image that can be burned to a CD-ROM and then Sneaker-Netted to those unconnected computers.

This DVD5 ISO image file contains the security updates for Windows released on Windows Update on March 12, 2013. The image does not contain security updates for other Microsoft products. This DVD5 ISO image is intended for administrators that need to download multiple individual language versions of each security update and that do not use an automated solution such as Windows Server Update Services (WSUS). You can use this ISO image to download multiple updates in all languages at the same time.

The March 2013 Security Updates ISO image is available at the Microsoft Download Center and weighs in at 3GB.