This is stated in The Guardian’s investigation, Ukrinform reports.

As the investigation showed, senior staff of the massive nuclear waste repository concealed the fact of the hack and its possible consequences.

The article notes that facility management does not know for sure when their IT systems were first attacked. The hack was first discovered in 2015, when experts realized Sellafield’s computer networks contained malware that could be used to spy or attack systems, according to the publication’s sources.

It is unknown whether the malware was successfully destroyed. This could mean some of Sellafield’s most sensitive activities, such as transporting radioactive waste, monitoring hazardous materials leaks and controlling fires, have been compromised, the newspaper said.

Their sources suggest it is likely that foreign hackers have gained access to sensitive materials at the facility, which is one of the most dangerous in the world.

This facility is home to the largest repository of plutonium on the planet, as well as a storage site for nuclear waste from weapons programs and decades of nuclear power. Contingency plans are also kept under police guard at Sellafield and will be used in case the UK suffers an external attack or disaster.

The UK’s Office of Nuclear Response (ONR) confirmed that Sellafield did not meet cyber standards, but refused to comment on the breach or allegations that the hack had been “concealed”.

As Ukrinform reported, at the end of November, the Japan Aerospace Exploration Agency (JAXA) announced that hackers had gained access to its computer system. They fear a possible leak of personal data of employees and other people.