Failed to fetch http://security.ubuntu.com/

Error

Failed to fetch http://security.ubuntu.com/ubuntu/dists/karmic-security/main/binary-amd64/Packages 

Solution:

1. Open /etc/apt/sources.list

2. Replace security.ubuntu.com with old-releases.ubuntu.com

So the new link looks like the following:

http://old-releases.ubuntu.com/ubuntu/dists/karmic-security/main/binary-amd64/Packages