However these big four companies are only part of a vast, sophisticated system of mass surveillance.

In this network are thousands of data brokers, ad agencies and technology companies - some of them Australian. They harvest data from millions of people, often without their explicit consent or knowledge.

Currently, this includes data related to the COVID-19 pandemic. For instance, data giant Palantir has provided lab test results and emergency department statuses to the US Centres for Disease Control and Prevention.

Data companies gather data about our online activity, location, DNA, health and even how we use our mouse. They use a range of techniques, such as:

This expansive tracking generates billions of data points that can reveal every facet of our lives including our family status, income, political affiliation, interests, friendships and sexual orientation.

Data companies use this information to compile detailed individual consumer profiles. These are used for purposes such as targeting us with ads, determining our eligibility for loans and assessing the riskiness of our lives.

Some of the world's largest data companies operate in Australia. Quantium is an Australian data analytics firm that acquires data from various partners including NAB, Woolworths (which owns 50 per cent of the company) and Foxtel.

These partnerships allow Quantium to "tap into the consumer data ecosystem with an unrivalled picture of the behaviours of more than 80 per cent of Australian households, spanning banking, household and retail transactions".

A company spokesperson told The Conversation most of its work is "data science and AI (artificial intelligence) work with first-party de-identified data supplied by the client". From this, Quantium delivers "insights and AI/decision support tools" for clients.

Anonymised or "de-identified" data can still be accurately re-identified. Even if a person's details are de-identified by being converted to an alphanumeric code, the conversion method is identical across most companies.

Therefore, each code is unique to an individual and can be used to identify them within the digital data ecosystem.

With a revenue of more than US$110 million last year, the insights from Quantium's data seem to be proving valuable.

From this revenue, more than A$61 million between 2012 and 2020 came from projects commissioned by the Australian government. This includes two 2020 engagements:

Quantium's spokesperson said they could not discuss the details of the contracts without government approval.

In the past decade, the Australian government has commissioned dozens of projects to other data analytics firms worth more than A$200 million.

These include a A$13.8 million Debt Recovery Service project with Dun & Bradstreet and a A$3.3 million National Police Checks project with Equifax - both started in 2016. It's unclear what and how much data has been shared for these projects.

Last year, the ACCC named Quantium as one of the companies that participate in the exchange of loyalty schemes data, often without consumers' explicit consent.

Quantium's spokesperson told The Conversation the company "does not deal with personally identifiable information and does not share data with any third party whether identified or de-identified".

Data companies largely operate in the shadows. We rarely know who has collected information about us, how they use it, who they give it to, whether it's correct, or how much money is being made from it.

LiveRamp (formerly Acxiom) is a US-based company partnered with Australia's Nine Entertainment Co. This partnership allows the Nine Network to give marketers access to online and offline data to target consumers across Nine's digital network.

This data may include the Australian electoral roll, to which LiveRamp gained access last year.

Similarly, Optum is a US-based health data company that collects information from hospital records, electronic health records and insurance claims.

It has data on more than 216 million people and used this to develop a predictive algorithm that was shown to discriminate against black patients.

The prevalence, scope and stealth of the abovementioned data practices are not congruent with the basic principles of a liberal democracy.

According to philosopher Isaiah Berlin, liberal democracies can only thrive if they have autonomous citizens with two types of freedoms:

Our data-driven world signals an extreme diminishing of both these freedoms. Our freedom of choice is harmed when our informational environments are doctored to nudge us towards behaviours that benefit other parties.

Our private space is all but gone in a digital environment where everything we do is recorded, processed and used by commercial and governmental entities.

Although our ability to disconnect from the digital world and control our data is eroding rapidly, there are still steps we can take to protect our privacy.

We should focus on implementing legislation to protect our civil liberties. The Australian Consumer Data Right and Privacy Act stop short of ensuring the appropriate data protections. The Australian Competition and Consumer Commission highlighted this in its 2019 report.

In 2014, the US Federal Trade Commission recommended legislation to allow consumers to identify which brokers have data about them - and that they be able to access it.

It also recommended:

If we care about our freedoms, we should try to ensure similar legislation is introduced in Australia.