software time lock and web access control

[Bruno Wolff III]

On Mon, Jun 13, 2011 at 07:21:46 -0500,
  Javier Perez <pepebuho at gmail.com> wrote:
> 
> I know maybe a combintion of IPTABLES and probably SQUID should do the
> trick, but

You can probably just use iptables and a cron job. iptables has a way to
check packets associated with particular users. So you should be able to
block common ports used for web traffic or all traffic not destined for the
local network for particular users.