Harm reduction on the dark web

The deep web is the part of the Internet that search engines do not index: email, databases, intranets, anything behind a password. Almost all of it is ordinary and harmless.

The dark web is a small part of the deep web that can only be reached with specific software, such as the Tor browser, which hides the location of whoever publishes and whoever visits. It hosts news outlets, whistleblower drop boxes and also drug cryptomarkets. Spanish-speaking forums often call all of it the “Red Profunda”.

A cryptomarket is a trading website on the dark web: you reach it through Tor, pay in cryptocurrency and encrypt messages with PGP. Vendors and buyers rate each other, as on any online shop.

Silk Road, opened in 2011, was the first large drug cryptomarket. The FBI shut it down in October 2013, and since then every police closure has been followed by users migrating to new markets: Silk Road 2.0, Evolution, AlphaBay and many more (Global Drug Policy Observatory, 2021).

In April 2013 Dr Fernando Caudevilla registered on the Silk Road forum under the alias he already used at Energy Control, DoctorX, and opened a thread called Ask a medical expert about health and drugs. Unlike almost everyone else there, he used his real identity from the start.

Over the next two years he answered questions on Silk Road, Silk Road 2.0 and The Hub forum: interactions between drugs and medicines, adverse effects, dependence, less harmful ways of using. By his own records, more than 900 questions answered and more than 130,000 views of his threads. Motherboard called him “The Dark Net’s Drug Counselor”.

In May 2015, ahead of Ross Ulbricht’s sentencing, his defence filed Dr Caudevilla’s sworn statement on harm reduction on Silk Road (The New York Times, 19 May 2015).

A selection of his cryptomarket questions from 2013 to 2017, reviewed and updated, is in The DoctorX Files.

Harm reduction starts from a fact: some people are going to use drugs, and the health priority is that they do so with as little harm as possible and without moral judgement. On the dark web that means taking information and health services to where buyers already are: the cryptomarket forums.

The literature calls it netreach, the online equivalent of street outreach workers: professionals who take part in user communities, answer questions, spread alerts about adulterated substances and bring drug checking closer (Vale Pires, Caudevilla and Valente, Adiktologie, 2016).

DoctorX has done this since 2013. In 2024 he was a moderator of the harm reduction forum on Dread, one of the dark web’s forums.

In 2014 Energy Control, the Spanish harm reduction NGO Dr Caudevilla worked with for almost twenty years, launched an international drug checking service aimed at cryptomarket users. Anyone who wanted to know what they had really bought sent a sample and received the laboratory result.

Dr Caudevilla was first author of the study of its pilot year: 219 samples tested. In 91.3% the main substance was the advertised one and most samples were of high purity; even so, 39.8% of cocaine samples contained levamisole, a veterinary deworming drug (Caudevilla et al., International Journal of Drug Policy, 2016).

Between 2014 and 2019 the service tested 5,879 samples from users worldwide. In 2015 it received four samples sold as heroin on cryptomarkets that contained ocfentanil, a synthetic opioid of roughly the same potency as fentanyl; the study, which he co-authored, described it as an adulterant (Quintana et al., International Journal of Drug Policy, 2017).

This page does not explain how to buy, and it does not recommend markets or vendors. It does summarise what testing has shown. Most of what is sold on cryptomarkets contains what is advertised, at high purity — but not always:

• Adulterants. Vendor ratings lower the risk but do not remove it: four in ten cocaine samples in the 2016 study contained levamisole.
• Very dangerous adulterants. The ocfentanil found in cryptomarket heroin is a very potent opioid; its use has been linked to severe effects and at least one death.
• Variable purity. In the same study cocaine averaged 72% purity and MDMA pills 133 mg, but with wide differences between samples. That makes dosing harder.
• New psychoactive substances. Forty different substances were advertised; some with very little information on dose and effects.
• Legal and privacy risks. Receiving controlled substances by post can be a crime, and markets close or vanish with their users’ money.

Testing the substance at a drug checking service, and being able to talk to a health professional without fear of judgement, reduces much of this risk.

Yes. The consultation is private, by video call and by appointment, in Spanish or English. Nobody will judge you for using drugs or for how you get them: the goal is your health. If you would rather make first contact encrypted, you can write using his PGP key.

Consultations do not recommend markets or vendors.

By Dr Fernando Caudevilla.

Silk Road Marketplace opened in 2011, the first large drug cryptomarket. Using technology that was already available — the Tor browser, cryptocurrencies such as Bitcoin (and later Monero), and encryption systems like GPG — it made anonymous drug trading possible, and in its users’ view safer than buying on the street.

Nobody would have bet on a platform that brought drug buyers and sellers together Amazon-style, running on reputation and trust. Heroin, MDMA or cannabis could be ordered comfortably from home and arrive in the letterbox a few days later. Around the figure of Dread Pirate Roberts, Silk Road’s enigmatic administrator, a virtual community of more than a hundred thousand people formed worldwide. Arresting him and shutting the site down became an international priority.

In October 2013 the FBI arrested Ross Ulbricht, a 29-year-old accused of being the brain behind Silk Road. In 2015 he was sentenced to two life terms — on charges that included drug trafficking and money laundering — for creating and running a website from his laptop. The judge justified the severity of the sentence by the need to deter anyone tempted to imitate him.

She got that wrong.

By then its successors, such as Silk Road 2.0 and Evolution, were already running. AlphaBay ran between 2014 and 2017 and, according to the FBI, grew to roughly ten times the size of Silk Road (NPR, 20 July 2017).

Every “police success” has been followed by an immediate migration of sellers and buyers to new platforms, each simpler to use than the last.

The model Silk Road inaugurated is the first exercise in regulating controlled drugs in a hundred years. Platforms of this kind are not necessarily the only, or the best, possible answer to the War on Drugs. But experience shows there is no going back on technological progress.

Although drug trading over the Internet is a minute fraction of the global trade, the trend is clearly upward. The Internet has the potential to revolutionise drug trafficking — and the drug policies that sustain it — with the same impact it has had on the record industry, film and television, or tourism.

The cryptomarket model also allows innovative, imaginative forms of preventive intervention to be tested. A significant part of my professional career has been spent on this ground.

Update: in January 2025 Ross Ulbricht received a presidential pardon in the United States.

• The DoctorX Files: over 900 real questions asked on cryptomarkets between 2013 and 2017.
• El Submarino del DoctorX: the blog on the history, economics and pharmacology of dark web markets (in Spanish).
• Meet DoctorX: his story in his own words.
• Press and talks about DoctorX.

Publications

• Caudevilla F, Ventura M, Fornís I, Barratt MJ et al. Results of an international drug testing service for cryptomarket users. International Journal of Drug Policy 2016; 35: 38–41. doi:10.1016/j.drugpo.2016.04.017
• Quintana P, Ventura M, Grifell M, …, Caudevilla F et al. The hidden web and the fentanyl problem: detection of ocfentanil as an adulterant in heroin. International Journal of Drug Policy 2017; 40: 78–83. doi:10.1016/j.drugpo.2016.10.006
• Caudevilla F. The emergence of deep web marketplaces: a health perspective. In: EMCDDA, The internet and drug markets (EMCDDA Insights 21), 2016.
• Vale Pires C, Caudevilla Gálligo F, Valente H. Netreach work: implementing web-based harm reduction interventions with online drug users. Adiktologie, 2016.
• Horton-Eddison M, Shortis P, Aldridge J, Caudevilla F. Drug cryptomarkets in the 2020s: policy, enforcement, harm, and resilience. Global Drug Policy Observatory, Policy Brief 16, 2021.

His story has also been turned into a novel: Doctor X. El médico de la Dark Web, by José Ángel Mañas and Jordi Ledesma (La Esfera de los Libros, 2024).