Debian 7 “Wheezy” Is managed by the LTS (Long Term Support) team. Who are responsible for security updates on wheezy until May 2018. To continue to receive updates you will need to update your sources.list.

vi /etc/apt/sources.list

Add the following to your sources.list file

deb http://httpredir.debian.org/debian/ wheezy main contrib non-free
deb-src http://httpredir.debian.org/debian/ wheezy main contrib non-free

deb http://security.debian.org/ wheezy/updates main contrib non-free
deb-src http://security.debian.org/ wheezy/updates main contrib non-free

deb http://httpredir.debian.org/debian/ wheezy-updates main contrib non-free
deb-src http://httpredir.debian.org/debian/ wheezy-updates main contrib non-free

Next update and upgrade your distro.

sudo apt-get update

sudo apt-get upgrade

Source

https://wiki.debian.org/LTS/
https://wiki.debian.org/LTS/Using