Co-funded by the European Union

The present glossary provides a non-technical and easy-to-understand list of the key concepts and ideas underlying the PROTON project. References are available at the bottom of the page.

Agent-based model

Agent-based models are “a [social] simulation that offers the possibility of modelling individual heterogeneity, representing explicitly agents’ decision rules, and situating agents in a geographical or another type of space” (Gilbert, 2007, p. 1). They are “computer programs [that provide] a simplified representation of “social reality” that serves to express as clearly as possible the way in which one believes that reality operates” (2007, p. 2). Of note, “A major advantage of agent-based modelling is that the difficulties in ensuring isolation of the human system and the ethical problems of experimentation are not present when one does experiments on virtual or computational systems” (2007, p. 3).


Bitcoin is a type of unregulated digital currency that was first created in 2008. Its intention is to bypass government currency controls and simplify online transactions by getting rid of third-party payment processing intermediaries. Bitcoin transactions are stored and transferred using a distributed ledger on a peer-to-peer network that is open, public and anonymous.

Criminal career

The term criminal career is defined as “the characterisation of a longitudinal sequence of offenses committed by an individual offender” (Blumstein, Cohen, Roth, & Visher, 1986, p. 12).

Dark Web

The Dark Web is a part of the Deep Web only accessible by special protocols and tools built on top of standard Internet protocols. Examples are TOR and I2P (see below). The common theme for these tools is the use of cryptography and sophisticated data routing technologies to hide the contents and flow of communication over the Internet. They all address a well-known vulnerability of the surface web, namely the ability to reveal a user’s identity and activities by simple traffic review and more sophisticated traffic analysis.

Darknet Markets

Dark Net Markets are virtual markets that are typically hosted as Tor hidden services. They look and feel like large online retailers providing a service between buyers & sellers transacting in Bitcoin or other cryptocoins. The most famous dark net market was Silk Road 1 which pioneered such an anonymous business model in 2011. More recent markets are known under such names as DreamMarket, Agora, Valhalla, etc.

Deep Web

In the security world and mainstream media, the term “Deep Web” means that it is not indexed by search engines, and is a place with much more content than the “standard” Internet (World Wide Web) or Surface Web that everyone uses.

Drug trafficking organisation

The term drug trafficking organisation refers to an organised criminal group as per the definition of the U.S. Department of Justice (U.S. Department of Justice, 2010, p. 10): “complex organisations with highly defined command-and-control structures that produce, transport, and/or distribute large quantities of one or more illicit drugs.”


The term embeddedness refers to the concept that individuals’ social contexts and relations (e.g. family ties, friendship ties, professional ties, criminal ties) influence their decisions and actions. As discussed by Granovetter (1973, 1983, 1985), individuals’ behaviour is affected by the strength of interpersonal ties, intended as the “combination of the amount of time, the emotional intensity, the intimacy, and reciprocal service” (Granovetter, 1973, p. 1361). In this regard, strong ties imply for instance frequent interactions and strong emotional intensity with others, though weak ties may be more valuable as they provide the individual with access to new information resulting from connections with acquaintances. For these reasons, the social environment in which the individuals are embedded plays a major role for their choices, actions, and ultimately also for their involvement in organised crime.


The term gang refers to a criminal group as per the definition of Langston (Langston, 2003, p. 2): “a group of people following a common code of conduct, having common beliefs and identifiers, existing in a semi-structured organisation or hierarchy, and attempting to accomplish their goals through criminal activity.”

Machine learning

Machine learning uses algorithms and statistical models to solve a computational task, for example recognizing patterns in data. Machine learning algorithms use mathematical models for the computations. The parameters of these models are not engineered, but instead learned from training data through dedicated algorithms.


The mafias constitute one specific form of organised criminal group and are characterized by (i.) a remarkable longevity, (ii.) an organisational and cultural complexity highlighting the honour of their members and relying on the respect of the code of silence (i.e. omertà), and (iii.) the ability to control legitimate markets as well as to exercise a political dominion over their areas of settlement, frequently using private violence and simultaneously supplying protection.

Natural Languages Processing

Natural Language Processing (NLP) describes algorithms which are capable to process natural human language, both written and spoken. It unifies approaches from both linguistics and computer science. NLP approaches make use of pattern recognition and machine learning algorithms.

Onion Routing

Onion routing is a technique to anonymize internet-communication by encapsulating messages in layers of encryption, analogous to layers of an onion. The encrypted data is transmitted through a series of network nodes called onion routers, each of which “peels” away a single layer, uncovering the data’s next destination. When the final layer is decrypted, the message arrives at its destination. The sender remains anonymous because each intermediary knows only the location of the immediately preceding and following nodes.

Organised criminal group

The term organised criminal group as per the definition of the United Nations Convention against Transnational Organized crime (United Nations, 2000, p. 5) refers to: “a structured group of three or more persons, existing for a period of time and acting in concert with the aim of committing one or more serious crimes or offences established in accordance with this Convention, in order to obtain, directly or indirectly, a financial or other material benefit.”

Other criminal organisation

The term other criminal organisation refers to a residual category that includes all criminal organisations that do not fit the definitions of mafia, drug trafficking organisation, or gang. Other criminal organisation is intended as per the definition of Hagan (Hagan, 2015, p. 395): groups that “(i.) utilize violence or threats of violence, (ii.) provide illicit goods that are in public demand, and (iii.) assure immunity for their operators through corruption and enforcement.”

Pattern recognition

A technique to automatically discover patterns and regularities in data, which are used for classification tasks, e.g. clustering data sets. To find patterns in data, machine learning algorithms are applied frequently.


Psycholinguistics studies the interconnection between language and psychological aspects.


As per the definition of the European Commission (2006), radicalization is “the phenomenon of people embracing opinions, views and ideas which could lead to acts of terrorism”. Accordingly, radicalization includes both cognitive and behavioral dimensions, namely “opinions, views and ideas”, and “acts” respectively (McCauley & Moskalenko, 2017).

Recruitment to organised crime

The term recruitment refers to the different processes leading individuals to the stable involvement into organised criminal groups. This interpretation comprises individuals deliberately choosing to participate in criminal organizations, but also subjects socialised into criminal groups through family, friendship, and community relations. It also includes, but it is not limited to, the processes of formal or ritual affiliation exhibited by some organised criminal group. The term recruitment excludes individuals occasionally cooperating or co-offending with members of organised criminal groups, as they lack stability over time.

Recruitment to terrorism

According to the 2005 Council of Europe Convention on the Prevention of Terrorism, recruitment to terrorism is when someone has been solicited to “commit or participate in the commission of a terrorist offence, or to join an association of group, for the purpose of contributing to the commission of one or more terrorist offences by the association or the group”. In short, as per the European Commission (2014), “Recruitment to carry out terrorist offences”.

Routine activities and differential associations

  1. Routine activities are “generalized patterns of social activities in a society (i.e., spatial and temporal patterns in family, work, and leisure activities)” (Wikström, 2009, p. 1).
  2. Differential associations are “individuals with whom a person associates, and who supply definitions both favorable and unfavorable to deviant behavior” (Freiburger & Crane, 2008), with definitions being “one’s own attitudes or meanings that one attaches to given behavior” (Akers, 2001:195), or “orientations, definitions of the situation, and other evaluative and moral attitudes that define the commission of an act as right or wrong, good or bad, desirable or undesirable, justified or unjustified” (Akers & Sellers, 2009, p. 90).
  3. There is an important reciprocal relationship between routine activities and differential associations in which each affects the other (Bernburg & Thorlindsson, 2001). For example, changes in place of residence, employment, new friends etc. can lead to both “new opportunities for socialization and changed routine activities” (Laub & Sampson, 2009, p. 43).

Surface Web

The surface web is commonly referred to as the part of the Internet indexed by search engines such as Google. It comprises normal HTML data as well as data sources accessible without authentication, e.g., e-Banking websites, or other unspecified access tooling, e.g., specific SQL database access queries. According to different sources, the surface web comprises between 0.5% and 5% of all data accessible via the protocols underlying the Internet.


As per the definition of the PROTON consortium: “Terrorism is the unlawful use of violence or threat of violence against persons, as well as serious damage or threats to property, critical infrastructure or systems, carried out by non-state actor organizations, members or supporters of such organizations, small groups or individuals who are motivated by religious, political, or other ideological beliefs, and aim to instill fear in and coerce governments or societies in pursuit of the furtherance, advancement or promotion of goals that are usually political, social, religious or ideological.”


Tor was originally designed, implemented and deployed in 2004 as a third-generation onion routing project of the U.S. Naval Research Laboratory. Developed primarily to protect government communications, it’s now used every day for many purposes by the military, law enforcement agencies, journalists, activists and a wide variety of other civilians. Tor at its most basic level is a peer-to-peer (P2P) network that allows anonymous, encrypted communication from host to host. It can also serve as a proxy with exit points known as “exit nodes” to allow users to anonymously browse web pages on the World Wide Web. This offers moderate anonymity to anyone looking to hide their identity as well as encrypt communication back to their host computer or device.

Web crawler

A web crawler is a software system which is capable to automatically browse web pages and collect the data in order to analyse the content of these pages.


Akers, R. L., & Sellers, C. S. (2009). Criminological Theories Introduction, Evaluation and Application 5th edition Oxford: Oxford University Press.

Akers, R. L. (2001). Social learning theory. In Paternoster, R. & Bachman, R. (eds.), Explaining criminals and crime: Essays in contemporary criminological theory (pp. 192–210). Los Angeles: Roxbury.

Bernburg, J. G., & Thorlindsson, T. (2001). Routine activities in social context: A closer look at the role of opportunity in deviant behavior. Justice Quarterly, 18(3), 543-567.

Blumstein, A., Cohen, J., Roth, J. A., & Visher, C. A. (1986). Criminal careers and “career criminals” (National Research Council (U.S.) Panel on Research on Criminal Careers). Washington, DC: National Academy Press.

Council of Europe. (2005). Convention on the prevention of terrorism. CETS No. 196. Warsaw.

European Commission. (2006). Terrorist Recruitment: A Commission’s Communication Addressing the Factors Contributing to Violent Radicalisation. MEMO/05/329. Brussels

European Commission. (2014). Report from the Commission to the European Parliament and the Council on the implementation of Council Framework Decision 2008/919/JHA of 28 November 2008 amending Framework Decision 2002/475/JHA on combating terrorism, COM 554. Brussels

Freiburger, T., & Crane, J. S. (2008). A Systematic Examination of Terrorist Use of the Internet. International Journal of Cyber Criminology, 2(1).

Gilbert, N. (2007). Agent Based Models. Thousand Oaks: Sage Publications.

Granovetter, M. (1973). The Strength of Weak Ties. American Journal of Sociology, 78(6), 1360–1380.

Granovetter, M. (1983). The Strength of Weak Ties: A Network Theory Revisited. Sociological Theory, 1, 201–233.

Granovetter, M. (1985). Economic Action and Social Structure: The Problem of Embeddedness. American Journal of Sociology, 91(3), 481–510.

Hagan, F. E. (2015). Introduction to Criminology: Theories, Methods, and Criminal Behavior. Los Angeles: SAGE Publications.

Langston, M. (2003). Addressing the Need for a Uniform Definition of Gang-Involved Crime. FBI Law Enforcement Bulletin, 72, 7.

Laub, J., & Sampson, R. J. (2009). Shared beginnings, divergent lives. Harvard: Harvard University Press.

U.S. Department of Justice. (2010). National Drug Threat Assessment 2010. Retrieved from

United Nations. (2000). Convention on Transnational Organized Crime (No. Assembly Resolution 55/95 of 15 Nov 2000). Retrieved from

Wikström, P.O.H. (2009). Routine Activities Theory, in Huebner, B.M. (eds.), Criminology. Oxford: Oxford University Press.