The National Crime Agency (NCA) is offering a $15 million reward for information that leads to the arrests of two ringleaders of the largest criminal ransomware network, Lockbit.

The UK effort has launched a revenge attack on Lockbit systems, obtaining stolen data. In addition, the two more masterminds involved in the group, a father-son duo, were arrested by police in Ukraine.

Lockbit appeared to admit responsibility for the attacks after the UK’s organised operation to recapture the data, posting a message on their website that said: “now under control of law enforcement”.

The operation has been dubbed the largest intervention into cyber attacks. Several blackmailed law enforcement agencies including FBI and Europol are stopping ransomware payments to other criminals.