打开 about:config, 修改下面这些项目:
network.proxy.type 1
network.proxy.socks 127.0.0.1
network.proxy.socks_port 1080
network.proxy.socks_remote_dns true
network.proxy.socks_version 5
network.proxy.no_proxies_on localhost, 127.0.0.1
0: Direct connection, no proxy. (Default in Windows and Mac previous to 1.9.2.4 /Firefox 3.6.4)
1: Manual proxy configuration.
2: Proxy auto-configuration (PAC).
4: Auto-detect proxy settings.
5: Use system proxy settings. (Default in Linux; default for all platforms, starting in 1.9.2.4 /Firefox 3.6.4)
Edit -> Preferences -> Advanced -> Network -> Connection -> Settings...