On a glibc system, in /etc/nsswitch.conf, for the 'hosts' database, assuming 'files' is the first source listed, comment out everything else if the argument to the 'hostsfilesonly' script is '1' or undo this if the argument is '0'. Besides that, the 'pause' script does the following: execute the 'hostsfilesonly' script with argument '0', wait for the amount of time indicated by the argument to the 'pause' script as defined by 'sleep(1)', execute the 'hostsfilesonly' script with argument '1', then kill all 'firefox' instances. Both scripts require root privilege, which may be configured as in the sample 'hostsfilesonly.sudoers' file..
This is useful as a very rudementary way for turning on/off browsing on a PC.