De

/msg dpkg flash

en el canal #Debian del FreeNode sabemos que:

<dpkg> it has been said that flash is frequently used to deliver interactivity, audio and video through a web browser.  Ask me about <gnash> or <swfdec> for free implementations or <adobe flash> for a non-free implementation.  See also http://wiki.debian.org/FlashPlayer

volviendo a preguntar:

/msg dpkg adobe flash

nos dice que:

<dpkg> Adobe Flash Player is <non-free> and cannot be in a stable Debian release, as Adobe doesn't provide security support for older versions (see http://bugs.debian.org/457291).  The easiest way to install flash is with the flashplayer-mozilla package from <debian-multimedia.org>; there is also a flashplugin-nonfree <contrib> package for sid and backports.org users.  Ask me about <dmm> <bpo> <non-free>.  http://wiki.debian.org/FlashPlayer

Checando la pagina sugerida:

http://wiki.debian.org/FlashPlayer

Sabremos que:

1. Agregamos el repositorio de los Backports:

[#] echo deb http://www.backports.org/debian lenny-backports main contrib non-free >> /etc/apt/sources.list

2. Importamos la llave:

[#] wget -O - http://backports.org/debian/archive.key | apt-key add -

3. Actualizamos:

[#] apt-get update && apt-get upgrade

4. Instalamos el plugin:

[#] apt-get install flashplugin-nonfree

5. Hacemos los cambios globalmente:

[#] /usr/sbin/update-flashplugin-nonfree --install

Desactivar el plugin de Debian

En el menu "Herramientas"->"Complementos" del Firefox (Iceweasel), en la sección "Complementos" podemos desactivarlo.

Enlaces externos:

• http://wiki.debian.org/FlashPlayer
  
   
• http://backports.org/dokuwiki/doku.php?id=instructions