40 percent of teenagers have hacked into social networking or banking accounts belonging to other people, says Trend Micro.
Research by the security firm also revealed that of the teenagers that admitted to hacking, boys were more likely to break into a social networking account in a bid to impersonate someone else while girls concentrated on hacking accounts to obtain money.
Trend Micro's Rik Ferguson said: "This is the online version of kids breaking into school to change their reports, it's just so much easier now".
"These results come as a stark warning to parents become a lot more familiar with what their kids get up to when online."
See also: 51% of kids surf the web unsupervised