v0.4.0

Changelog v. 0.4.0 (2021-July-22):

• Add an option to simulate a regular warden by defining a fraction of CCs that are blocked (by simply preventing their probe packets being sent. Made sure time consumption is similar to regular sending.
• Added option to simulate a regular warden.
• Added option to simulate a simplified adaptive warden.
• Remove unnecessary cs.h
• Put some macro checks in separate file so that some major configuration mistakes are caught.
• Tell the CR about the configuration (type of warden and its settings) so that it can be displayed when NEL phase is completed to ease the analysis process. This is useful in combination with a typescript (see script(1)).
• Fixed several (minor) bugs and performed code clean-ups; improved inline documentation.

v0.2.5

Network Environment Learning (NEL) Phase for Covert Channels (with a Feedback Channel).

In Network Steganography research, a covert channel is a stealthy communication channel. Some covert channels are capable of performing a so-called Network Environment Learning phase (or: NEL phase). Such covert channels can determine how data can be covertly exchanged in a way that countermeasures (firewalls, traffic normalizers, active wardens) can be bypassed.

For instance, a typical covert channel technique is to embed secret data in reserved or unused bits of protocol headers. A typical firewall filter could simply clear the bit to prevent such a covert channel. During the NEL phase, communicating covert channel peers can determine such a filter rule and switch to alternative covert channels.

Although the NEL phase was originally discussed in academia about ten years ago, no implementation was made available by other researchers. With NEL, we provide the first public implementation of a NEL phase on the basis of scapy and libpcap. NEL is written in C and runs best under Linux.

Documentation: Please have a look at the documentation.

CHANGELOG for the NEL tool

v. 0.2.5:

• slightly updated the markdown files (also pointed out the
  idea of the dynamic warden)
• performed some tiny improvements of the documentation