"A lot of the time you can't see the physical server, but you can go to the domain registrars and seize the domain. They're not using fancy electronic equipment or breaking Tor to unmask people. It's good old-fashioned policing," Professor Woodwood told Fairfax Media. The fall of these sites suggests law enforcement has a grip on the dark web. But do they? The Centre for International Governance Innovation (CIGI) recently called for intensified monitoring of the dark web by police and spy agencies. According to the think tank, recent revelations of government surveillance may trigger a fragmentation of the dark web into many "alternative dark nets", making investigations that are already tough far more complex. The Silk Road's operators used The Onion Router (Tor) to evade police for around two years. Tor is a privacy-enhancing network maintained by the Tor Project, funded by the US government. It is popular with people wanting to secure their anonymity online for privacy and or piracy reasons. Tor can conceal the location of a server used to run a hidden website. End-users can use the Tor browser to visit hidden websites in the dark web and also prevent third-parties from tracking what they do on the open web.

Tor is entirely legal and used by journalists, whistleblowers, people fearful of their government, military and police. Australians concerned by the data retention law can use it to thwart the collection of data about their internet activity tied to a particular IP address since Tor routes connections to a website through an intermediate IP address. But what happens when a major network on the open web, like Facebook, goes to the dark web? Last year the social network launched its own hidden website on Tor at to experiment with different modes of access (Tor link here). CIGI notes Facebook's hidden website could offer terrorist organisations a powerful propaganda tool that is encrypted, decentralised and anonymous. That's a world away from Facebook and Twitter on the open web where privacy is non-existent. "You should not assume that anything you put on social media is something that you wouldn't put in the newspaper the next day," Professor Woodward said.

Tor has become synonymous with the dark web, but it's far from the only network for anonymous communications. GNUnet is a service for file transfers, while Tox offers anonymous messaging. Networks with similar features to Tor include HyperBoria and I2P (Invisible Internet Project). They all rely on a similar architecture to provide anonymity, but H.D. Moore, chief researcher at security firm Rapid 7, says the scale of each separates them. "The size of the network is hugely important for anonymity. Tor is the only clear winner here," he told Fairfax Media, adding that the recent dark web seizures in Europe and the US were likely a fraction of services operating there. Professor Woodward concurred with this view. "My guess is that the number of dark web stores and services is still higher than ever," Mr Moore said. So what of data retention? If websites on the dark web are run by humans who make mistakes, shouldn't the mass collection of user data help police investigations down the track?

Not really. "Most, if not all, of these services are typically run without identifying logs. Tor, by default, does not log the IP addresses of the peers that connect to it," Mr Moore. said "While the Tor directory servers and relays are public, there is no way to comprehensively track communication inside the network, especially for services that use onion routing. Data retention laws are unlikely to be of use to law enforcement and in fact may be harmful to consumers overall - that data has to be stored somewhere and makes a juicy target for hackers." Follow IT Pro on Twitter