Phones with touch screens vulnerable to 'smudge attacks'

The study also found that “pattern smudges,” which build up from writing the same password numerous times, are particularly recognizable.

“We showed that in many situations full or partial pattern recovery is possible, even with smudge ‘noise’ from simulated application usage or distortion caused by incidental clothing contact,” the paper said. 

The researchers said their next project may be to investigate if heat trails on touch screens could create similar vulnerabilities.