Knoppix 7.5

Security and Privacy

Security and protection of privacy are the top priorities of the Knoppix architecture. The popular Firefox Web browser – known as "Iceweasel" in Debian – is equipped with an "armed" NoScript plugin. With just a few exceptions, Iceweasel alerts for any website that has active content (e.g., certain JavaScript or Adobe Flash content that could have a negative effect on the security and stability of the browser) and tries to access plugins or the local hardware by displaying a corresponding message and waiting for confirmation or rejection by the user.

The yellow alerts above the status bar at the bottom of the browser point to what could be technically problematic content. The user can then decide whether to unlock the website permanently for this session only, or not at all, for active content (e.g., for viewing Flash videos or launching plugins that enable the camera, microphone, or other hardware components). NoScript makes banking and payment transactions when shopping on the Internet far more secure; it also identifies many cross-site scripting attacks and detects and warns the user of what it considers to be "suspicious" or poorly programmed scripts on web pages.

Tor (The Onion Router) is a privacy expansion designed to protect the privacy of users, who are often spied on by websites or ads with a tracing feature. It can be enabled in Firefox and Chromium with a simple start script and one-click proxy settings.

To use Knoppix as a virus scanner for Windows malware, the Knoppix boot menu offers a starter for the ClamAV scanner. Its first action is naturally to update the malware database via the network.

 

TCP Stealth (Experimental)

As a Live system, Knoppix is a practical platform for testing new and experimental features. One of these is TCP Stealth [1]. This TCP modification, which is described in an IETF draft [2], is used for authorization when opening a connection; it is sent with the first SYN packet (i.e., before data transfer between the client and server takes place). Although the authorization uses a relatively weak key length and is therefore not suitable as a substitute for challenge-response authentication with strong encryption, it can make it difficult to scan for open ports. After all, packages without the correct passkey are rejected (i.e., the port scanner "does not see" the services running on the scanned ports).

The Knock kernel patch [3] is required for this procedure to work. It makes new socket options available, and the sockets can, in turn, be used for authorized access by server and client programs. Knoppix 7.5 not only has the kernel patch, but also an SSH server and client with TCP Stealth support. To enable this, you only need to set the TCPStealthSecret option and a password for client authorization in /etc/ssh/sshd_config:

TCPStealthSecret "1234"

After starting the SSH server (ssshstart in Knoppix), a connection is still not possible. Despite the SSH server running on port 22, a port scanner finds only a black hole (Listing 1).

Listing 1

No SSH Server on Port 22

 

If the client is now configured to transfer the authorization token when establishing the connection, by adding the same TCPStealth configuration option to /etc/ssh/ssh_config, the port can now be opened, and an SSH login is possible:

$ ssh localhost
knoppix@localhost's password:

as shown in this example.

Knoppix PXE Boot Server

Knoppix can be configured as a boot server for the local network so that other computers are booted as clients of the server and have remote read-only access to the disk mounted in Knoppix. In contrast, programs are executed locally on the client. To this end, the KNOPPIX menu has the KNOPPIX terminal server option. The configuration is very simple: Essentially, you only need to confirm the desired IP range for your clients and any deviating boot options. It is thus possible to operate a whole classroom from a single Knoppix USB stick or DVD.

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