Having recently made two-factor authentication available for Google Apps customers, Google on Thursday extended its more secure sign-on mechanism to all Google Accounts.

Google calls the process two-step verification. It is intended to reassure those who believe they need more than a mere password standing between their online data and the cyber-thieves of the world.

"Two-step verification requires two independent factors for authentication, much like you might see on your banking Web site: your password, plus a code obtained using your phone," explains Google product manager Nishit Shah in a blog post.

The set-up process isn't ridiculously onerous, but it isn't drop-dead easy either. Google suggests setting everything up may take 15 minutes. Thoughtfully, users aren't entirely on their own: Google provides a set-up wizard to guide people through the necessary steps.

Turning two-step verification on is done through the "Using 2-step verification" link on the Google Account Settings page. Users who don't see any such link can expect it to be available within the next few days.

Once enabled, a user who signs in with the Account password will be presented with an extra Web page asking for a code. Google will either generate an automated call with the code, send the code to a mobile phone via SMS, or allow the user to generate the code using an app on an Android, BlackBerry or iPhone device.

A particularly convenient feature is the ability to register a backup phone to receive codes, in case one's primary phone get stolen or is lost.

Additional security, however, should not be confused with foolproof security. In late 2009, Gartner issued a research note recommending further defenses beyond two-factor authentication. It seems cyber-thieves have had some success bypassing two-factor security schemes at some banks using man-in-the-middle attack techniques. The fraudsters managed to have verification phone calls associated with compromised accounts forwarded to their own phones.

But Google's decision to offer extra security to those who want it represents a step in the right direction.

Matt Cutts, who runs Google's Web spam team, notes that two of his relatives have had their Gmail accounts hijacked because someone guessed their passwords.

"If someone hacked your Gmail account, think of all the other passwords they could get access to, including your domain name or Web host accounts," he wrote in a blog post.

While conceding that the extra security of two-step verification may be an inconvenience, he insists it's worth the trouble. "I use it on my personal Gmail account, and you should too," he said.