Microsoft Security Essentials is the latest Antivirus and Antispyware released by Microsoft which is free to use for lifetime. I have been using this Antivirus for quite some time now and am very pleased with its performance.
The definition update for this is released almost daily and to update to the latest signatures, it needs the internet connection. What if you don’t have an internet connection? No problem solution is mentioned below.
To install the definition updates offline and without the internet you need to download the Microsoft Security Essentials virus and spyware definition update file, from these:
These files are executables that would update the MSE with the latest signatures available.