Browsing the web with Tor
NixOS packages the Tor Browser Bundle, which is the recommended way to browse the web using Tor. Install the tor-browser-bundle-bin package and run tor-browser. The browser bundle integrates its own Tor daemon and will handle connecting to the Tor network automatically.
Enabling Tor as a system service
Tor can be enabled as a system service by enabling options
By default Tor in NixOS provides one SOCKS proxy on port 9050. 9050 is a "slow" SOCKS port which can be used for email, git and pretty much any other protocol but HTTP(S) since a new circuit will be created for each destination IP. This is a safe default which complicates identity correlation attacks, although isn't sufficient to completely thwart them.
By also enabling
services.tor.client.enable, an additional SOCKS service on port 9063 can be enabled. This is a "fast" SOCKS port suitable for browser use; a new circuit is established every ten minutes.
By default, the Privoxy HTTP proxy is enabled if you enable Tor client functionality (
services.tor.client.enable). Privoxy listens on port 8118 and is configured to route to the fast SOCKS port. It is highly advisable to route HTTP traffic via Privoxy rather than via SOCKS directly.
Tor wrappers: torsocks, torsocks-faster and tsocks
Tor wrappers such as torsocks and tsocks can be used to intercept network API calls in applications to direct network activity over a Tor socks port. This allows non-Tor-aware, non-SOCKS-aware applications to have their traffic routed over Tor.
torsocks is slightly more secure than tsocks because it blackholes UDP traffic and private IP traffic, such as LAN traffic.
If you choose to use a wrapper, use torsocks where possible. Use torsocks-faster/the fast port/Privoxy for HTTP or protocols which break if used from several IPs (such as ICQ or FTP).
tsocks is the weakest wrapper, but it is necessary if your application needs to make local connections or makes DNS queries in a way not handled by torsocks. For example, Kopete's XMPP plugin only works with tsocks and leaks DNS queries.
Some applications have native support for SOCKS proxies, and it is tempting to use such support. However, it isn't unheard of for proxy support to have bugs or for application plugins to ignore proxy settings or for settings to get lost. Using a wrapper such as torsocks can be more reliable.
An alternative approach is use both a wrapper and built-in proxy support. This way, if the application's proxy support fails, the connection is likely to be caught by the wrapper and if you run the application without the wrapper by mistake, the connections are still likely to be proxied.
Using KDE with Tor
In KDE, proxy server configuration is set for all applications centrally. You should set the SOCKS proxy to Tor's default SOCKS port (127.0.0.1:9050), and set the HTTP proxy to Privoxy (127.0.0.1:8118).
Without Privoxy, KDE applications using either KHTML or WebKit KPart (such as Konqueror, Rekonq, KTorrent, Akregator) would become nearly unusable and cause excessive load to the Tor network.
Another possibility is to run tsocks kdeinit4, which would cause kdeinit4 to respawn in a wrapped state. All KDE applications started after this will be wrapped with tsocks.
Kopete makes direct connections and ignores KDE settings. Kopete torification dependins on what plugins you use. XMPP requires tsocks. ICQ requires torsocks-faster.
KMail respects KDE-wide proxy settings, and the "safe" SOCKS port offers good isolation between mailboxes.
Tor Browser in a Container
You can also run the Tor Browser in a Container.