Four people suspected of committing online crimes, including malware writing, data theft and credit card fraud, have been arrested in Spain.

Police in Alicante arrested two seventeen year olds yesterday and charged the pair with creating a Trojan horse, which officers claim allowed them to remotely take control of webcams on infected computers within local educational institutions.

It's claimed that this enabled the duo to spy on students and record intimate images, which they then used to blackmail the victims into giving them money.

According to reports, later that day police in Madrid arrested two adults in connection with the earlier inquiry. Authorities suspect the men used the teenagers to obtain confidential information in order to commit credit card fraud. They allegedly made purchases amounting to almost £41,000 (60,000 Euros) using fake credit card details.

Reports said that the investigation - named Praxis - has been ongoing since August 2005, when a Spanish computer science company became a victim of the hacking attack. That same year, in a separate case, the courts fined a Spanish male computer student for spying on a woman via her webcam and monitoring her online communications.

Carole Theriault, senior security consultant at Sophos, said in a statement: "Whether it's done for financial gain or for dubious personal reasons, spying on others using webcams is a sick and twisted thing to do, and likely to traumatise the innocent people that suffer this invasion of privacy.

"The two individuals charged with creating the Trojan may be minors, but this is no schoolboy prank - these criminals were in it for the money, and were prepared to blackmail and steal from their peers, as well as selling on personal information so that other wrongdoers could get in on the act."

Authorities in Spain have offered a free disinfectant tool for people with compromised computers.

Theriault added: "It's encouraging to see the Spanish authorities responding to the concerns of businesses and home computer users, and actively pursuing the perpetrators of all online criminal behaviour.

"In this case, if found guilty, the Spanish courts need to dish out a tough sentence to all parties, in order to send out the message that this type of online behaviour will not be tolerated."