Darknets — the often seamy counterparts of the internet that are accessible only through special programs that help to ensure privacy and anonymity — may be far more resilient to attack than the internet, a new study finds.

Darknets are computer networks of hidden services. The most popular darknet, and the one that most people think of, is the Tor network. This network has become infamous for sordid activity such as drug sales and pedophile rings, although it does have more respectable applications too, such as protecting journalists from repressive regimes and helping police carry out sting operations.

Researchers at the U.S. Naval Research Laboratory and the Defense Advanced Research Projects Agency originally developed the core principles of Tor in the 1990s. The aim of Tor was to protect government communications online, and the U.S. government and others continue to help fund Tor to this day. [How Big Is the Internet, Really?]

The often-illegal nature of activities on the Tor network has made sites on it targets of attacks to shut them down or compromise the anonymity of its users.In a new study, scientists in Spain wanted to learn more about how this key darknet worked and how resilient it was to attacks compared to the internet.

The researchers analyzed how about 5,000 to 6,000 nodes — essentially, Web pages — in the Tor network were linked by about 275,000 to 2 million connections between 2013 and 2015. Next, they compared these structures with how about 46,000 to 50,000 nodes in the internet were linked by about 195,000 to 221,000 connections during that same time.

The scientists noted that the internet has a backbone of hubs that are tightly connected to one another. This kind of collection of hubs is known as a "rich club" because it resembles groups such as Ivy League alumni organizations that help their members connect with one another. Previous research has found that similar "rich clubs" of neurons likely help the human brain orchestrate higher mental functions, and failures of such connections might lead to problems such as Alzheimer's disease.

In contrast, the Tor network lacked a rich club. Basically, the internet is a centralized network that makes it easy to run and search for online services, whereas Tor is a very decentralized network.

"The internet is designed to maximize speed and performance, whereas the darknet is designed to maximize anonymity," said study lead author Manlio De Domenico, a physicist at Rovira i Virgili University in Tarragona, Spain.

However, the decentralized nature of the Tor network makes it far more resilient than the internet to targeted attacks and random failures, the researchers said. In contrast, taking down members of the rich club of the internet can destabilize the whole system. For instance, they noted that the internet needed about 90 percent of its nodes to keep operating, whereas the Tor network could still operate even if a random failure knocked out 40 percent of its nodes.

"This amount of robustness in the darknet is exciting because it is an emergent property of this system — it was not designed for this purpose," De Domenico told Live Science.

These findings suggest that even sophisticated attacks can only slowly dismantle a darknet, the researchers noted. "More research will be required to understand how to better attack this type of networked system," De Domenico said.

De Domenico and his colleague Alex Arenas, also ofRovira i Virgili University, detailed their findings online Feb. 27 in the journal Physical Review E.

Original article on Live Science.