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README.md

Automata-based Detection of Network Anomalies

Detano toolsuite is tailored for learning probabilistic automata (Alergia algorithm with extensions) and anomaly detection in ICS networks based on probabilistic automata.

Installation

To run the tools you need to have installed Python 3.9 or higher with the following packages

  • dataclasses
  • bidict
  • bitarray
  • numpy
  • scipy
  • FAdo for Python 3

These packages you can install using the pip3 util. Or you can use the provided requirements.txt file (all dependencies can be installed via pip3 install -r requirements.txt). In order to generate the documentation, run doxygen in the doc folder.

Tool Support Overview

All tools in the suite works with probabilistic automata obtained from a list of messages (packets) divided into conversations (messages that logically belong together). Messages (packets) are assumed to be provided in a csv file (each message per line). Files containing message are then input of the tools below. The tools also allow to work with conversations given as an input. Currently supported protocols are IEC 104 and MMS (if the messages are given as an input, only IEC 104 is supported).

Tools are located in the directory src.

  • anomaly_check.py Tool for a detection of anomalies in a csv file (testing file) based on a given valid traffic sample (training file). Based on the particular method, a PA/PTA is first obtained from training file. The detection mechanism then checks whether conversations differs from the testing file. Currently supported approaches include detection based on comparing distributions and detection based on single conversation reasoning.
  • pa_learning.py Learning of PA based on own implementation of Alergia (including the testing phase) and learning based on prefix trees (PTAs). As an input it takes a csv file containing messages.

Supporting rules are placed in directory units (run with python3 -m units.conv_splitter <params>).

  • window_extract.py Extract conversations from a give range of time windows. The script takes a .csv file together with the number of the first and the last window, and returns parsed conversations belonging to each window.

Program documentation is placed in directory doc (to generate the documentation run doxygen in doc directory).

Input Data Format

The list of messages is assumed to be provided in an IPFIX csv file, one message per line with the following columns:

TimeStamp;Relative Time;srcIP;dstIP;srcPort;dstPort;ipLen;len;fmt;uType;asduType;numix;cot;oa;addr;ioa

As an example, see files from Dataset repository or the following:

TimeStamp;Relative Time;srcIP;dstIP;srcPort;dstPort;ipLen;len;fmt;uType;asduType;numix;cot;oa;addr;ioa
15:03:10.31;0.000000;192.158.2.111;192.158.2.248;55000;2404;58;17;0x00000000;;122;1;13;0;63535;64537
15:03:10.31;0.000595;192.158.2.248;192.158.2.111;2404;55000;63;19;0x00000000;;120;1;13;0;63535;64537

The list of conversations is assumed to be provided in a csv file, one conversation per line, given as

Timestamp;Relative Time;Duration;Length;Data
Key;<src IP>-<dest IP>-<src port>-<dest port>;

where data is a comma separated sequence of messages. For the case of IEC 104, a message is represented by a pair <asduType.cot>, for the case of MMS, a message is represented by a pair <MMStype.service>. For instance

Timestamp;Relative Time;Duration;Length;Data
Key;192.158.2.100-192.158.2.101-2404-55000;
13:20:51.45;2.562578489;0.212390052;706;<100.6>,<100.7>,<1.20>,<100.10>

Anomaly Detection

The anomaly detection approaches implemented within the tool anomaly_check.py takes as an input a file capturing valid network traffic and a file containing traffic to be inspected. Format of input files is described above. Examples of csv input files can be found in Dataset repository. More specifically, detection approaches (based on distribution comparison or single conversation reasoning) can be run as follows:

  • anomaly_check.py <valid csv file> <inspected csv file> [OPT] where OPT allows the following specifications:
    • --atype=pa/pta learning based on PAs/PTAs (default PA)
    • --alg=distr/member anomaly detection based on comparing distributions (distr) or single message reasoning (member) (default distr)
    • --format=conv/ipfix format of input data: conversations (conv) or csv data in ipfix format (ipfix) (default ipfix)
    • --smoothing use smoothing (for distr only)
    • --reduced=val remove similar automata with the given error upper-bound val [0,1] (for distr only)
    • --threshold=val find malicious conversations from windows having distance higher than val
    • --help print a help message

Automata Learning

Approaches for learning of probabilistic automata in the context of industrial networks are implemented within the tool pa_learning.py. The tool takes as an input a file capturing network traffic. Examples of csv input files can be found in Dataset repository. More specifically, the tool can be run as follows:

  • pa_learning.py <csv file> [OPT] where OPT allows the following specifications:
    • --atype=pa/pta learning based on PAs/PTAs (default PA)
    • --format=conv/ipfix format of input file: conversations/IPFIX (default IPFIX)
    • --help print a help message

Example of Use

First, download datasets from Dataset repository. The benchmark contains datasets in IPFIX format, capturing various anomaly scenarios. Example of the anomaly detection:

$ ./anomaly_check.py ../../datasets/scada-iec104/attacks/normal-traffic.csv ../../datasets/scada-iec104/attacks/scanning-attack.csv --atype=pa --alg=distr --smoothing --format=ipfix
Automata counts:
192.168.11.248:2404 -- 192.168.11.111:61254 | 4

Detection results:
../../datasets/scada-iec104/attacks/normal-traffic.csv ../../datasets/scada-iec104/attacks/scanning-attack.csv

192.168.11.248:2404 -- 192.168.11.111:61254
0;0.0
1;0.0
2;0.0
3;0.0
4;0.0
5;0.0
6;0.0
...

The Automata counts part shows the number of automata models used for each communication pair. The Detection results part then shows concrete output of the detection for each communication pair and each time window in the testing traffic (numbered from 0) in the form of <window>;<detection output>.

Example of the automata learning:

$ ./pa_learning.py ../../datasets/scada-iec104/attacks/normal-traffic.csv --atype=pa --format=ipfix
File: normal-traffic.csv
alpha: 0.05, t0: 13
States 3
Testing: 0/25233 (missclassified/all)
Accuracy: 1.0

The output shows used learning parameters, the number of states of the learned DPA and the accuracy. The learning uses first 33 % of the input traffic for learning and the rest for accuracy evaluation (this value can be changed directly in the file pa_learning.py).

Automata Format

PAs are specified using a format, which given as follows.

<initial state>
(<source state> <destination state> <symbol> <probability>)*
(<final state> <probability>)*

Structure of the Repository

  • src Source codes of the tool support
  • doc Source code documentation
  • experimental scripts for evaluation

Publications

The tool suite is based on the following papers:

  • Efficient Modelling of ICS Communication For Anomaly Detection Using Probabilistic Automata. Petr Matoušek, Vojtěch Havlena, and Lukáš Holík. In Proceedings of IFIP/IEEE International Symposium on Integrated Network Management. ISBN 978-3-903176-32-4. 2021 (pdf)

Contact

If you have a question, do not hesitate to contact the authors:

  • Vojtěch Havlena <ihavlena at fit.vutbr.cz>
  • Petr Matoušek <matousp at fit.vutbr.cz>
  • Lukáš Holík <holik at fit.vutbr.cz>