The Defence Forces has said it did not purchase surveillance software from a controversial hacking company, which itself has been hacked.

Data, which it is claimed was stolen by hackers from Italian based firm Hacking Team, appeared online on Sunday and the company's Twitter account was also compromised.

Hacking Team makes surveillance software used by governments to tap into phones and computers.

The company has previously been accused by anti-surveillance campaigners of selling snooping tools to governments with poor human rights records.

Among the 400GB of emails, passwords, product source code and internal files posted online earlier this week were four emails between a Hacking Team employee and a number of Defence Forces personnel.

The first, dated 3 July 2012, is from a Defence Forces employee to Hacking Team's Key Account Manager Massimiliano Luppi, which attempts to organise a follow up meeting after the two met in Prague that month.

The next dated 16 April 2014, from Mr Luppi to two members of the Defence Forces, refers to a meeting at the end of 2013.

Mr Luppi writes: "During our meeting at the end of last year, you anticipated [sic] me that the process of purchasing a solution like ours would have started in spring of 2014.

"I was wondering if you now have a clearer idea of the process and situation".

The third email sent to Mr Luppi from one of the Defence Forces members on 14 December 2014 claims that he has been posted overseas, and that the other Defence Forces member who had been party to the correspondence has retired.

However, the email continues, "...we have planned to attend Prague ISS and will introduce some new friends to you at that point, so keep some time free if you can and we'll bring you you [sic] to speed then."

On its website ISS World Europe, which takes place in Prague, describes itself as "the world's largest gathering of European Law Enforcement, Intelligence and Homeland Security Analysts as well as Telecom Operators responsible for Lawful Interception, Hi-Tech Electronic Investigations and Network Intelligence Gathering."

The last email, dated 28 May this year, from the Defence Forces member who had previously been corresponding with Mr Luppi, states: "Looking forward to meeting you next week."

It is not clear from the released documentation whether there was further email correspondence between the parties in the interim periods or if they met last month as suggested.

In a statement the Defence Forces said that for operational security reasons it cannot comment on specific elements of the questions submitted to it by RTÉ News.

But it did confirm that no services were purchased from the company in question.

Hacking Team has confirmed the breach of its systems took place and that it is being investigated by law enforcement authorities.

It has recommended that clients suspend use of its software until it works out whether specific law enforcement operations have been exposed.

Other documents which it is claimed came from the company's servers identify alleged current and former clients from several European countries, the FBI, the US Drug Enforcement Administration and police and state security organisations in countries with records of human rights abuses such as Egypt, Ethiopia, Kazakhstan, Morocco, Nigeria, Saudi Arabia and Sudan.

Hacking Team was named one of five private-sector "Corporate Enemies of the Internet" in a 2012 report by Reporters Without Borders.

Citizen Lab, a digital rights research group affiliated with the University of Toronto, has published numerous reports linking Hacking Team software to repression of minority and dissident groups, as well as journalists in a number of countries in Africa and the Middle East.