Police swooped on homes in Huddersfield today as part of a nationwide crackdown on cyber crime.

Houses in the town were raided, along with others in West Yorkshire, in a major operation targeting hackers.

Police investigating the sale of computer software that allows users to steal information from other people’s computers are continuing to visit a number of addresses across West Yorkshire as part of a crackdown on cyber-criminality.

Nine addresses across the county, including homes in Leeds, Bradford and Huddersfield have been visited after spyware, which allows the user to hack into someone else’s computer and steal information, including pictures and videos, was traced to someone living at each address.

More than 40 arrests have been made this week by the National Crime Agency’s Cyber Crime Unit at more than 20 separate locations across England, Wales and Scotland as part of a week of activity targeting cyber crime.

Andy Archibald, deputy director of the NCA’s National Cyber Crime Unit, said: “Behind this week’s activity is the message that all of us, as individuals, businesses or law enforcement agencies, have a role to play in making the UK a safe place to enjoy the huge opportunities provided by the internet.

“Awareness of the type of cyber crime dangers which are out there is vital, whoever you are, as is collaboration between organisations across different sectors, regions and countries to develop the most effective ways of combating those threats.

“We will continue to work with partners to pursue and disrupt the major crime groups targeting the UK, but also, crucially, to make the UK as difficult as possible a target for cyber criminals in the first place.”

One of the suspected hackers from Britain has been arrested in connection with an alleged cyber attack on the United States Department of Defence (DoD) as part of a week-long UK-wide operation.

The 23-year-old man was arrested on Wednesday by NCA officers in Sutton Coldfield, in the West Midlands, on suspicion of offences linked to data stolen from a messaging service used by DoD employees around the world.

Although it’s not illegal to purchase spyware you are committing an offence if you use it to access someone else’s data without their permission.

In West Yorkshire, Det Inspr Vanessa Smith, who is leading the operation, said: ‘‘Officers are in the process of visiting the addresses of people we believe have purchased a specific type of spyware that enables them to steal information from other people.

‘‘These visits and the accompanying letter is known as a Cease and Desist Notice and involve officers speaking to those who’ve ordered the software and making them aware of the legislation around their use.

‘‘During the last year we’ve seen national and international news following the theft and redistribution of personal information, including pictures and videos. This rapidly expanding area of criminality can leave victims extremely emotionally distressed and open to blackmail as well as financial theft.’’

Officers believe many young people, including a number of teenagers, are thought to be buying the spyware and often using their parents’ bank accounts to pay for the software.

DI Smith said: ‘‘I know from other colleagues across the country that a number of parents’ have been completely unaware their children have bought spyware using money from their accounts. I would encourage parents and carers to regularly change any passwords to online accounts, including the addition of commas, hashes and asterisks and ask questions if their children have approached them to buy any type of computer software.”

Prosecutions from the use of malicious computer software can result in 10 years imprisonment.