Victor Bassilious: Public must be vigilant in face of latest attacks
Hacking is the unauthorised intrusion into these connected computer systems. The hacker's aims can really be anything from benign curiosity to illegal activities such as identity theft, pornography, financial theft or fraud.
With the wider use of the web and wireless systems, computers and mobile phones are now connected almost round the clock, putting them at constant risk from automated attacks. Sophisticated software known as botnets can search the connected world for vulnerable computers at very high speeds.
There is a new trend in cyber crime where groups are forming partnerships to increase their impact, such as Dogma-Koobface that attacks social networks such as Facebook, and ZeuS-SpyEye trojans that attack the banking online systems.
The impact of hacking cannot be easily calculated as it affects us not only financially but also emotionally. If you have a computer or a mobile phone that you use to connect to the world, you are at risk. To minimise this risk, the public need to be aware of the danger and be constantly vigilant to the techniques used.
The government estimates cyber crime costs the UK economy about 27 billion a year; in February - other estimates count the global cost to be in the region of 600bn a year.
The recent arrests have all been generally young people. They are clever, they have access to hacking tools and, with some little knowledge, they can do some degree of harm. They are suspected of "revenge" attacks as a kind of civil disobedience or sending a message to specific organisations like PayPal.
The attacks do not look like they are coming from a more organised action group with criminal intent. However, if people have committed a crime, they are subject to the law.
• Victor Bassilious is a senior lecturer in internet computing at Abertay University in Dundee.