The Mariposa botnet had the power to dwarf Georgia and Estonia cyberattacks if it had been used to launch denial of service attacks, say Spanish police.

Months of investigations by the Guardia Civil in Spain, the FBI and security firm Panda Security and Defence Intelligence led to the takedown of the 12.7 million strong zombie network in December and the arrest of three suspects in Spain two months later.

At a press conference announcing the operation in Madrid on Wednesday, Spanish police said they recovered the personal details of 800,000 people from systems recovered from three alleged cybercriminals. This cache of stolen information includes bank login credentials from businesses and consumers as well as email passwords.

Three Spanish residents suspected of running the botnet have been charged with online offences: the most senior alleged botmaster, nicknamed “Netkairo”, 31, from Balmaseda in the spanish province of Vizcaya, as well as his two alleged lieutenants JPR, 30, from Molina de Segura Murcia and JBR, 25, from Santiago de Compostela in La Coruña. None of the suspects have been named at this stage of proceedings.

In a statement (in Spanish here), Guardia Civil officers said they were also on the trail of a fourth suspect nicknamed Phoenix, who’s possibly based in Venezuela.

Defence Intelligence discovered the botnet last May and formed a team that brought in security experts from Bilbao-based Panda and computer scientists at Georgia Tech Information Security Center. Security researchers infiltrated the botnet’s command and control systems, learning enough to mount a successful takedown operation in cooperation with ISPs on 23 December.

Netkairo responded to this by launching a retaliatory denial of service attack against Defence Intelligence that took out customers at a Canadian ISP for several hours. In wrestling to obtain control of the botnet he made the mistake of connecting to compromised systems using his home PC, a mistake that led to his identification (as explained in our earlier story on the takedown operation).

Luis Corrons, technical director of PandaLabs, explains the Mariposa botnet’s business model and the takedown operation in a video below. ®