Three teenagers were arrested today on suspicion of computer hacking linked to attacks on companies perceived as enemies of whistleblowing website Wikileaks.
The three boys aged 15, 16 and 19, were arrested with two men, aged 20 and 26 in coordinated arrests.
The Metropolitan Police said: "The arrests are in relation to recent and ongoing 'distributed denial of service' attacks (DDoS) by an online group calling themselves 'Anonymous'.
"They are part of an ongoing MPS investigation into Anonymous which began last year following criminal allegations of DDoS attacks by the group against several companies.
"This investigation is being carried out in conjunction with international law enforcement agencies in Europe and the US."
Detectives from the Met's Police Central e-Crime Unit (PCeU) arrested the five at 7am at addresses in the West Midlands, Northants, Herts, Surrey and London.
All five have been taken to local police stations where they remain in custody.
Anonymous made the headlines last year when the group launched "Operation Payback", attacking companies that withdrew services from WikiLeaks.
The "hacktivists" targeted such brands as Visa, Mastercard and PayPal.
The distributed denial of service attacks use software designed to illegally access a computer and can be done with minimal knowledge.
Hacktivists flood their target's server so it is overloaded and unavailable for legitimate users.
Under UK law it is a criminal offence to carry out "any unauthorised act in relation to a computer" where the person "has the requisite intent and the requisite knowledge" to do it.
The maximum penalty is 10 years behind bars and a £5,000 fine.