A cyber attack on Scotland's environmental agency is entering its fourth week after already stealing 1.2GB of data last month.

Officials from Scottish Environement Protection Agency (SEPA) said on Thursday that the organisation is still under cyber-attack and that key operations have been shut down.

Since Christmas Eve, criminals have stolen about 1.2 GB of confidential data in an attempt to extort money from the agency.

The four thousand files include personal information about SEPA staff, contract and procurement documents, pollution permits, enforcement notices and commercial work with overseas agencies.

READ MORE: Cyber criminals post stolen data

Terry A'Hearn, SEPA chief executive, said that the agency will not pay the ransom demanded by the hackers. He believed that the attackers were international cybercriminals who picked SEPA specifically.

A'Hearn said that SEPA are still working with the Scottish Government, Police Scotland and the National Cyber Security Centre to solve the issue.

Much of the data has been published online by the attackers, while some of it was already available to the public. SEPA said that they may never know the true extent of the theft.

A'Hearn added: "Sadly we’re not the first and won’t be the last national organisation targeted by likely international crime groups.  We’ve said that whilst for the time being we’ve lost access to most of our systems, including things as basic as our email system, what we haven’t lost is our twelve-hundred expert staff. 

"Through their knowledge, skills and experience we’ve adapted and since day one continued to provide priority regulatory, monitoring, flood forecasting and warning services. 

"Whilst some systems and services may be badly affected for some time, step-by-step we’re working to assess and consider how we recover.  We’ll issue a broader update on service delivery and recovery early next week, with weekly updates to be clear on what those we work with can expect and how we’ll prioritise progress."