Criminals and terrorists are using the so-called dark net to buy weapons, a new study has suggested.
Those selling the illicit weapons often disassembled and sent them in different packages or embedded them in old stereos or printers, the report found.
Researchers found that firearms and related goods generated 136 sales per month and a monthly revenue of $80,000 (£62,000).
The firearms trade has gained attention following recent terrorist attacks.
The dark net is a part of the internet that requires specific software to access, in order for users to remain anonymous.
While the trade was unlikely to fuel large-scale terrorist operations, it had the potential to become the platform of choice for “lone-wolf” terrorists to obtain weapons and ammunition, the report said.
Non-profit organisation Rand Corporation Europe, working with Manchester University, found 52 unique vendors selling weapons or similar items such as ammunition, explosives, or components such as silencers across 811 listings and 18 markets.
Police believe the 2016 Munich shooting, which left nine people dead, used weapons purchased on the dark net.
Lead author of the research, Giacomo Persi Paoli, said: “Recent high-profile cases have shown that the threat posed by individuals or small groups obtaining weapons illegally from the dark web is real.
“The ability to not only arm criminals and terrorists, who can make virtually anonymous purchases, but also vulnerable and fixated individuals is perhaps the most dangerous aspect.”
Guns account for less than 1% of items sold on the platform, with its main trade being in narcotics.
Nevertheless, the volume being sold “can be considered sufficiently high to be a cause of concern for policy makers and law enforcement agencies”, said the report.
The study involved collecting data from 12 dark net marketplaces during a week in September 2016.
Most of those selling guns were based in the US, but Europe was the most popular destination for the weapons they sold.
Judith Aldridge, co-investigator on the study, said: “In very simple terms, anyone can connect to the dark web and within minutes have access to a variety of vendors offering their products, which are most often illegal.
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“The dark web enables illegal trade at a global level, removing some of the geographical barriers between vendors and buyers, while increasing the personal safety of both buyers and sellers through a series of anonymising features that obscure their identities.”