Update Microsoft Security Essentials Offline

you need to Install the latest Microsoft Security Essentials definition updates for get protection against newest
viruses and threats and updating MSE ( Microsoft security essentials ) require working internet connection but , you can also update your MSE offline you have to download and install latest definitions from microsoft site and install them as administrator 

download for 32 bit : http://go.microsoft.com/fwlink/?LinkID=87342

download for 64 bit : http://go.microsoft.com/fwlink/?LinkID=87341

• If your computer is running Windows Vista or Windows 7,  Right-click Mpam-fe.exe, click Run as administrator, and then click Yes. When you are prompted for an administrator password or confirmation, type the password or provide confirmation, and then wait while the definition files are installed.
• If your computer is running any other Windows operating system, you must be logged on as an administrator to install the latest definition file. Browse to the folder where you saved the file, and then double-click Mpam-fe.exe to install the latest definition file.
• Note: If you do not have an administrator account on the computer, ask an administrator to log on and install the definition file for you.

If you are running Microsoft Security Essentials build 2.0.0375.0 or higher,

download and install the Network Inspection System definition updates for 64 bit 

download and install the Network Inspection System definition updates for 32 bit 

for Network Inspection System for computers running an x64-based version of Windows.