European crime agency Europol has announced the arrest of two suspected members of the Distributed Denial of Service for Bitcoin (DD4BC) hacking collective.
DD4BC first gained notoriety in 2014, and is thought to be responsible for a number of successful cyber extortion and denial-of-service (DoS) campaigns against European companies in exchange for bitcoins.
Key members of the group were identified in Bosnia and Herzegovina by the UK Metropolitan Police Cyber Crime Unit which provided "vital information" to the investigation, according to Europol.
The arrests - made as part of a takedown termed Operation Pleiades - were made on 15 and 16 December last year, and Europol claimed to have picked up the mastermind behind the hacking collective and an accomplice.
Police also searched the suspects' homes and found "an extensive amount of evidence".
"Law enforcement and its partners have to act now to ensure that the cyber space affecting nearly every part of our daily life is secure against new threats posed by malicious groups," said Wil van Gemert, Europol's deputy director of operations, after the arrests.
"These groups employ aggressive measures to silence the victims with the threat of public exposure and reputation damage. Without enhanced reporting mechanisms, law enforcement is missing vital means to protect companies and users from recurring cyber attacks.
"Police actions such as Operation Pleiades highlight the importance of incident reporting and information sharing between law enforcement agencies and the targets of distributed DoS and extortion attacks."
The inter-agency operation, initiated by Austria, was supported by Europol's European Cybercrime Centre and the Joint Cybercrime Action Taskforce.
Authorities from Australia, France, Japan, Romania, the US and Switzerland also took part in the investigation.
DD4BC has launched a number of extortion campaigns since mid-2014, usually targeting the online gambling, financial services and entertainment industries.
Europol warned that paying the ransom risks "appearing vulnerable" and being targeted again for an even higher amount.
Extorting money through social engineering, targeted ransomware and hacking is on the rise, according to Sean Sullivan, a lead researcher at security firm F-Secure.
This, alongside an increase in data breaches and the impact of legal reform, is predicted by security experts to affect the security industry over the course of 2016.
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