Pattern locks on Android can be a simpler way of locking your phone. However, like a PIN or password, some patterns can be easier to guess than others. To stay secure, avoid using shapes that look like letters and stick to patterns that use five or more of the nine nodes.
Security researcher Marte Løge of the Norwegian University of Science and Technology explains how not all patterns are created equal. In an analysis of 4000 patterns that test subjects created, most patterns used only four or five of the nine nodes. However, the fewer nodes you use, the fewer possible combinations there are and the easier it is to guess. She also found that 10 per cent of the patterns created were shaped like a letter of the alphabet, typically after the initial of a spouse or child.
Of course, some of these conclusions are purely interesting from a maths and security research perspective. For example, if someone steals your phone, they have no idea how many nodes you used, so the number of potential possibilities isn't really relevant for pure guesswork. However, it also highlights that certain patterns are more obvious than others. Using a pattern in the shape of a letter, for example, is not much better than using a PIN of 1234. The more complex your pattern is, while avoiding common patterns like letters, the harder it will be for someone to guess their way into your phone. Check out the source link for a more detailed breakdown on what makes a strong pattern.