People should stop using patterns to unlock their devices, researchers have warned. A new study has found that it’s a lot easier for people who might be looking over your shoulder as you unlock your phone to memorise a pattern than a passcode. So-called “shoulder surfing attacks” can be easy for a criminal to plan and execute, but you can protect yourself by switching to a PIN code and increasing its length from four digits to six, the researchers say. They got over 1,000 volunteers to act as attackers, challenging them to memorise a range of unlocking authentications – four- and six-digit PINs, and four- and six-length patterns with and without tracing lines – by watching a victim over their shoulder from a variety of angles. The 5-inch Nexus 5 and 6-inch OnePlus One were the two handsets used in the study, as the researchers say they “are similar to a wide variety of displays and form factors available on the market today, for both Android and iPhone”. The researchers also considered single and multiple views for the attacker and two different hand positions for the victim – single-handed thumb input and two-handed index-finger input.
The study found that four-length patterns with visible lines were far easier to crack, as a result of shoulder surfing, than any other type of unlocking authentication they tested. “We find that PINs are the most secure to shoulder surfing attacks, and while both types of pattern input are poor, patterns without lines provides greater security,” the researchers, from United States Naval Academy and the University of Maryland, said. “The length of the input also has an impact; longer authentication is more secure to shoulder surfing. Additionally, if the attacker has multiple-views of the authentication, the attacker’s performance is greatly improved.”
In tests, 10.8 per cent of six-digit PINs were cracked after one observation. This figure rose to 26.5 per cent after two observations. 64.2 per cent of six-length patterns with tracing lines, meanwhile, were cracked after one observation. This rose to 79.9 per cent after two observations. 35.3 per cent of six-length patterns without tracing lines were cracked after one viewing, rising to 52.1 per cent after two viewings. “Shorter patterns were even more vulnerable,” said the researchers, who added that even people who use fingerprint or face-scanning technology to unlock their phones should be ary of their findings. “Biometrics are a promising advancement in mobile authentication, but they can be considered a reauthenticator or a secondary-authentication device as a user is still required to have a PIN or pattern that they enter rather frequently due to environmental impacts (e.g., wet hands),” they said.
“There are also known to be high false negatives rates associated with biometrics. Further, users with biometrics often choose weaker PINs as compared to those without, suggesting that the classical unlock authentication remains an important attack vector going forward.”
A separate study published earlier this year found that the majority of lock patterns can be cracked within five attempts.