A freedom of expression group has launched a list of “digital predators”, ranking what it says are 20 of the world’s worst offenders for cyber-censorship and orchestrated online repression.

Published on Thursday by Reporters Without Borders (RSF) to coincide with World Day Against Cyber-Censorship, the list names and shames entities around the globe whose activities it regards as “tantamount to preying on journalism”.

It documents state and non-state actors allegedly responsible for what the group describes as “a clear danger for freedom of opinion and expression” guaranteed by article 19 of the Universal Declaration of Human Rights.

RSF classifies the digital predators under four broad headings: harassment, state censorship, disinformation and spying or surveillance. The inventory includes authoritarian regimes and private-sector companies, based in western countries such as the US, UK, Germany and Israel, specialising in software that can be used for targeted cyber-espionage.

“The authoritarian strongmen behind predatory activity against press freedom are extending their tentacles into the digital world with the help of armies of accomplices, subordinates and henchmen who are organised and determined digital predators,” said Christophe Deloire, RSF’s secretary general.

“We have decided to publish this list of 20 digital predators in order not only to expose another aspect of press freedom violations but also to draw attention to the fact that these accomplices sometimes act from or within democratic countries.

“Opposition to despotic regimes also means ensuring that the weapons for suppressing journalism are not delivered to them from abroad,” he added, referring to British, German and Swiss companies allegedly involved in supplying intrusive software to abusers.

While some of the entities and methods listed – such as those linked to the Kremlin, Tehran and China – are well documented, including the aggressive use of troll farms, online spying and disinformation, the report describes how such digital control methods are becoming more and more widespread.

Among case studies documented is that of Rana Ayyub, an Indian journalist who wrote the Gujarat Files, a book about Narendra Modi’s rise to power, and who has become a prominent target of “Yoddhas” – online trolls who either volunteer their services or are paid employees of the ruling Hindu nationalist Bharatiya Janata party.

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The report also focuses on the alleged existence of a “hate office” in the administration of Brazil’s president, Jair Bolsonaro. First revealed by Joice Hasselmann, a parliamentarian and former ally of Bolsonaro, the office reportedly consists of presidential advisers and is coordinated by the president’s son, Carlos. It publishes attacks against journalists on a large scale, including Glenn Greenwald, the former Guardian journalist, now of the Intercept, who has published revelations about Bolsonaro.

The report also looks at the state-sponsored social media “reinformation” campaign run by Vietnam’s ministry of public security. An army of 10,000 cyber-soldiers, its ostensible role is to combat online “abuses” and “reactionary forces” – in reality meaning those opposed to the government.

It gives as an example a deadly raid on a village known as Dong Tam in January this year, in which the actions of the police were widely criticised. Social media was flooded with forced confessions from those accused of being involved, apparently in an effort to distract criticism.

Also on the list is Zerodium, a US-based cybersecurity firm that, according to RSF, obtains information about vulnerabilities in widely-used software from hackers and security researchers before selling it on to third parties.