In Spain, police arrested three suspected members thought to have carried out online attacks on several companies, most notably MasterCard and Sony.
According to the Bloomberg newswire, as part of their probe of the hacktivist group, police had to overcome "complicated security measures taken by its members to protect its anonymity.
Luis Corrons, Panda Labs' technical director, said that Spanish police released a screenshot dated May 18 showing a number of targets attacked by the Anonymous group, including Spain's central electoral board and the Police Corps website.
"The Spanish Police have announced on Twitter the arrest of `three leaders of the Anonymous group in Spain. These arrests have taken place in Barcelona, Alicante and Almeria. According to police sources, the alleged Anonymous members were decision makers and were involved in the recent attacks. Also, police agents have seized one of the servers used in many of the attacks in Gijon (Northern Spain)", he said in a weekend blog posting.
Corrons warned, however, that the internet is very likely to see some kind of retaliation actions from Anonymous, "as they are used to getting away with their actions and these arrests are surely very bad news for them."
As the weekend wore on, the Turkish police announced that that they too had made arrests - a total of 32 people thought to be Anonymous hactivistsm says the AP newswire.
The newswire added that the arrests followed attacks on websites operate by Turkey's telecommunications watchdog, the prime minister's office and the parliament.
It remains to be seen what extent the Anonymous hactivists were involved in their targeted attacks. As reported back in January, however, Anonymous hacktivists were widely noted as starting to use IRC channels to co-ordinate their DDoS attacks
This may have been the group's downfall, Infosecurity notes, as the international Echelon computer network routinely scans all IRC channels for `interesting' traffic, and passes this information, where appropriate, to Interpol plus national police agencies.