Although it is illegal in some parts of the world, 12 percent of U.S. and U.K. respondents to an Accenture survey have logged on to someone else's unsecured Wi-Fi connection.

Data that is sent via unsecured wireless routers is unencrypted and could theoretically be read by anyone who had the right network sniffing tools, but many people have tried logging on to unsecure Wi-Fi.

Logging on to open Wi-Fi signals is most popular with 18- to 34-year-olds, Accenture said. Nearly a third of them said they had done this at some point.

The practice is apparently more common in the U.S., where one in seven have piggybacked on free Wi-Fi networks, than in the U.K., where Accenture found that it was attempted by one in 11.

In some parts of the world, Wi-Fi piggybacking is considered to be a form of criminal hacking. In August, police arrested a 39-year-old man for using his laptop to connect to an unsecured Wi-Fi connection as he sat on a garden wall in the London suburb of Chiswick. And in a case that was widely publicized in the U.S., Sam Peterson of Sparta, Michigan, was charged after using a cafe's wireless connection to check his e-mail.

The Accenture study found that computer users are still engaging in some unsafe computing practices. Nearly half of all respondents said that they used the same password for all of their online accounts, and only a quarter of them have ever encrypted files on their computers.

Most computer users are sensitive to reports of identity theft, the study found, with about 25 percent of respondents saying that they would stop shopping at a retailer that had suffered a security breach. One-third said that they would continue to shop at the store, but would pay in cash rather than using credit or debit cards.

One other finding: People in the U.S. are more likely to keep their security software up-to-date than their U.K. counterparts. One in seven U.K. households never update security software. In the U.S., that ratio is 1-in-20.

Accenture's survey was based on telephone interviews with 800 U.S. and U.K. residents.