SAN FRANCISCO -- Google has been vacuuming up fragments of people's online activities broadcast over public Wi-Fi networks for the past four years, a breach of Web etiquette likely to raise more privacy worries about the Internet search leader.
Even Google was troubled by its behavior, and issued a public apology Friday. The company said it only recently discovered the problem in response to an inquiry from German regulators.
"Maintaining people's trust is crucial to everything we do, and in this case we fell short," Alan Eustace, Google's top engineering executive, wrote in a blog post.
Google characterized its collection of snippets from e-mails and Web surfing done on public Wi-Fi networks as a mistake, and said it has taken steps to avoid a recurrence.
About 600 gigabytes of data were taken off the Wi-Fi networks in more than 30 countries, and Google plans to delete it all as soon as it gains clearance from government authorities.
None of the information has appeared in Google's search engine or other services, according to Eustace.
Google's contrition may not be enough to allay growing concerns about whether the company can be trusted with the vast storehouse of personal information that it has gathered through its search engine, e-mail and other services.
Fears that Google is morphing into a real-life version of "Big Brother" have spurred previous privacy complaints as well as pleas for more stringent regulation of the company.
The Wi-Fi data was sucked up while Google expanded a mapping feature called "Street View" that also has pressed privacy hot buttons. Street View provides photographs of neighborhoods taken by Google cameras that have sometimes captured people doing things they didn't want to be seen doing, or in places where they didn't want to be seen.
As it set out to photograph neighborhoods around the world, Google equipped its vehicles with antenna as well as cameras so it could create a database with the names of Wi-Fi networks and the coding of Wi-Fi routers.
What Google didn't know, Eustace said, is that some experimental software was being used in the Street View project, and that programming picked up the Web surfing that occurred on publicly accessible Wi-Fi networks if the company's vehicles were within range of the signal.
Google gathered only small bits of information because its vehicles were on the move and its tracking equipment switched channels five times a second.