https://wiki.debian.org/iwlwifi

Debian 7 "Wheezy"

1. Add a "non-free" component to /etc/apt/sources.list, for example:

   # Debian 7 "Wheezy"deb http://http.debian.net/debian/ wheezy main contrib non-free

2. Update the list of available packages and install the firmware-iwlwifi package:

   # apt-get update && apt-get install firmware-iwlwifi

3. As the iwlwifi module is automatically loaded for supported devices, reinsert this module to access installed firmware:

   # modprobe -r iwlwifi ; modprobe iwlwifi

4. Configure your wireless interface as appropriate.