Protesters wearing the Anonymous Guy Fawkes masks that have become synonymous with the hacking group
The international police agency said the arrests were made in Argentina, Chile, Colombia and Spain as part of Operation Unmask, which was launched in mid-February.
The suspects, aged between 17 and 40, are believed to have planned coordinated cyber-attacks against institutions including Colombia’s defence ministry and presidential websites, Chile’s Endesa electricity company and national library among other targets.
Four of the 25 suspected anonymous hackers were arrested in Spain following attacks on Spanish political party websites.
They are suspected of defacing websites, carrying out denial-of-service attacks and publishing data on police assigned to the royal palace and the premier’s office online.
Interpol said the four included the alleged manager of Anonymous’ computer operations in Spain and Latin America, identified only by his initials and the aliases “Thunder” and “Pacotron”.
Two servers used by the group in Bulgaria and the Czech Republic have been blocked, according to a police statement.
All the arrests were carried out by national law enforcement officers working under the support of Interpol’s Latin American Working Group of Experts on Information Technology Crime.
Headquartered in Lyon, France, Interpol has no powers of arrest or investigation but it helps police forces around the world work together, facilitating intelligence sharing.
Anonymous’ origin can be traced back to a popular US image messaging board but the loose-knit group of hackers has become increasingly politicised.
Authorities in Europe, North America and elsewhere have made dozens of arrests and Anonymous has increasingly attacked law enforcement, military and intelligence-linked targets in retaliation.
One of the group’s most recent actions involved secretly recording a conference call between US and British cyber investigators tasked with bringing Anonymous to justice.
The group has no real membership structure. Hackers, activists and supporters can claim allegiance so it is unclear what impact the arrests will have.
Some internet chatter has appeared to point to a revenge attack on Interpol’s website.
One Twitter account purportedly associated with Anonymous’ Brazilian wing said the sweep would fail. “Interpol, you can’t take Anonymous. It’s an idea.”