The faces and behaviour of online avatars could help identify the people controlling them, scientists believe.
Using both characteristics, researchers hope to develop techniques for checking whether the digital characters are who they claim to be.
Such information could be used in situations where login details are not visible or for law enforcement.
Impersonation of avatars is expected to become a growing problem as real life and cyberspace increasingly merge.
Avatars are typically used to represent players in online games such as World of Warcraft and in virtual communities like Second Life.
As their numbers grow, it will become important to find ways to identify those we meet regularly, according to Dr Roman Yampolskiy from the University of Louisville.
Working out if their controller is male or female has an obvious commercial benefit, he said. But discovering that the same person controlled different avatars in separate spaces would be even more useful.