Anonymous has claimed responsibility for a cyber-attack against a US government website, resulting in the leak of sensitive employee data.

Members of the online activist collective Anonymous have taken credit for an attack on the United States Census Bureau website and the publication of data that includes employee names, email addresses, phone numbers and positions within the US government. The leaked data, which has been published online, also includes password hashes – which are difficult, but not impossible, to crack.

The US Census Bureau gathers data on every US resident once every 10 years, as well as data on its economy every five years. It's mission statement includes the line: "We honour privacy, protect confidentiality, share our expertise globally, and conduct our work openly."

The reason for the cyber-attack is the recent Trans-Pacific Partnership (TPP) and Transatlantic Trade and Investment Partnership (TTIP), both of which are top priorities for the Obama administration and promise a radical reform of the global politico-economic system, with integration and convergence of major Atlantic and Pacific nations. Among the many oppositions to the twin agreements is the way they have been drawn up in secret, with Anonymous being vocal in its opposition.

While the leak is far from the most serious the US government is dealing with at the moment – that would be the massive data breach affecting the Office of Personnel Management – it is nonetheless embarrassing.

The US Census Bureau has confirmed to IBTimes UK in an emailed statement that the attack took place and that it is looking into the matter, although it also pointed out that the information stolen was "non-confidential".

The US Census Bureau is investigating an IT security incident relating to unauthorised access to non-confidential information on an external system that is not part of the Census Bureau internal network. Access to the external system has been restricted while our IT forensics team investigates.

The statement went on to claim the department placed a high priority on security.

Security and data stewardship are integral to the Census Bureau mission. We will remain vigilant in continuing to take every necessary precaution to protect all information.