Back at the dawn of the Web, the most popular account password was “12345.”

Today, it’s one digit longer but hardly safer: “123456.”

Despite all the reports of Internet security breaches over the years, including the recent attacks on Google’s e-mail service, many people have reacted to the break-ins with a shrug.

According to a new analysis, one out of five Web users still decides to leave the digital equivalent of a key under the doormat: they choose a simple, easily guessed password like “abc123,” “iloveyou” or even “password” to protect their data.

“I guess it’s just a genetic flaw in humans,” said Amichai Shulman, the chief technology officer at Imperva, which makes software for blocking hackers. “We’ve been following the same patterns since the 1990s.”