Ars Technica reported on new data that uncovered the surprising predictability of Android lock patterns.

Now, Android lock patterns—the password alternative Google introduced in 2008 with the launch of its Android mobile OS—are getting the same sort of treatment. The Tic-Tac-Toe-style patterns, it turns out, frequently adhere to their own sets of predictable rules and often possess only a fraction of the complexity they’re capable of. The research is in its infancy since Android lock Patterns (ALPs) are so new and the number of collected real-world-patterns is comparatively miniscule. Still, the predictability suggests the patterns could one day be subject to the same sorts of intensive attacks that regularly visit passwords.

Marte Løge, a 2015 graduate of the Norwegian University of Science and Technology, recently collected and analyzed almost 4,000 ALPs as part of her master’s thesis. She found that a large percentage of them—44 percent—started in the top left-most node of the screen. A full 77 percent of them started in one of the four corners. The average number of nodes was about five, meaning there were fewer than 9,000 possible pattern combinations. A significant percentage of patterns had just four nodes, shrinking the pool of available combinations to 1,624. More often than not, patterns moved from left to right and top to bottom, another factor that makes guessing easier.

[…]

Data breaches over the years have repeatedly shown some of the most common passwords are “1234567”, “password”, and “letmein”. Løge said many ALPs suffer a similar form of weakness. More than 10 percent of the ones she collected were fashioned after an alphabetic letter, which often corresponded to the first initial of the subject or of a spouse, child, or other person close to the subject. The discovery is significant, because it means attackers may have a one-in-ten chance of guessing an ALP with no more than about 100 guesses. The number of guesses could be reduced further if the attacker knows the names of the target or of people close to the target.

This reminds me of how important and useful TouchID is. It is so easy to shoulder surf, even unintentionally. Don’t take my word for it. Be more aware when an Android user unlock their phone near you next time.