Now for some good news: During a week when Facebook and then Apple -- yes, Apple -- admitted getting hacked and a report tied the Chinese military to a major cyberspy gang targeting U.S. businesses and organizations, Google's security team said it has seen the number of compromised Gmail accounts drop 99.7 percent since 2011.

Mike Hearn, a Google security engineer, today blogged that Google's efforts to determine the legitimacy of log-ins has cut those email account hijackings since their peak in 2011. The secret sauce: using more of a risk analysis process and Google's multifactor authentication steps for Google user accounts. "Every time you sign in to Google, whether via your web browser once a month or an email program that checks for new mail every five minutes, our system performs a complex risk analysis to determine how likely it is that the sign-in really comes from you. In fact, there are more than 120 variables that can factor into how a decision is made," Hearn said in his post.

If a login attempt appears suspicious -- originating from a different country since a user's last login, for example -- Google prompts the user with a few questions. "For example, we may ask for the phone number associated with your account, or for the answer to your security question. These questions are normally hard for a hijacker to solve, but are easy for the real owner. Using security measures like these, we've dramatically reduced the number of compromised accounts by 99.7 percent since the peak of these hijacking attempts in 2011," Hearn says.

Google has witnessed some hefty account-hijacking attempts. In one case, a single user used stolen passwords to try to break into 1 million Google accounts a day for weeks at a time, according to Hearn. "A different gang attempted sign-ins at a rate of more than 100 accounts per second," he said, noting that Google's security system doesn't just check the password's validity in order to thwart these types of attacks.

Google recommends strong passwords for Google accounts, its two-step authentication option, and updating account recovery options.

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