Você pode obter o Firefox via ftp como detalhado na resposta do Suporte da Mozilla a uma pergunta semelhante intitulada Como faço para instalar Firefox em um computador sem navegador atual?
Matt Silverman também descreve isso em Como Faça o download do Firefox sem um navegador da Web .
Em qualquer caso, a ideia básica é, a partir da linha de comando, fazer o seguinte:
ftp
open ftp.mozilla.org
username: anonymous
password: anonymous
cd pub/mozilla.org/firefox/releases/latest/win32/en-US
ls
binary
lcd d:\folder (download destination)
get "Firefox Setup 22.0.exe"
(check that you have the Firefox Setup 22.0.exe file on the USB drive)
bye
Aqui está uma gravação de fazer isso em uma sessão real:
C:\>ftp
ftp> open ftp.mozilla.org
Connected to ftp.dynect.mozilla.net.
220-
220- ftp.mozilla.org / archive.mozilla.org - files are in /pub/mozilla.org
220-
220- Notice: This server is the only place to obtain nightly builds and needs to
220- remain available to developers and testers. High bandwidth servers that
220- contain the public release files are available at ftp://releases.mozilla.org/
220- If you need to link to a public release, please link to the release server,
220- not here. Thanks!
220-
220- Attempts to download high traffic release files from this server will get a
220- "550 Permission denied." response.
220
User (ftp.dynect.mozilla.net:(none)): anonymous
331 Please specify the password.
Password: anonymous
230 Login successful.
ftp> cd pub/mozilla.org/firefox/releases/latest/win32/en-US
250 Directory successfully changed.
ftp> ls
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
Firefox Setup 24.0.exe
Firefox Setup Stub 24.0.exe
226 Directory send OK.
ftp: 53 bytes received in 0.02Seconds 3.31Kbytes/sec.
ftp> binary
200 Switching to Binary mode.
ftp> get "Firefox Setup 24.0.exe"
200 PORT command successful. Consider using PASV.
150 Opening BINARY mode data connection for Firefox Setup 24.0.exe (22710720 bytes).
226 Transfer complete.
ftp: 22710720 bytes received in 137.84Seconds 164.76Kbytes/sec.
ftp> bye
221 Goodbye.
C:\>
Depois, basta executar o arquivo .exe
baixado para instalar o navegador.