Whenever a user connects to the Web via Wi-Fi, or even if their laptop's wireless systems are merely left turned on, someone using such a so-called sniffing tool can garner data about where the user has traveled, what type of operating system or applications they use, and who they may work for, Graham said.

For instance, the expert said that while sitting in airlines' business customer lounges it's not hard to look at details offered up freely by the machines of other travelers using Wi-Fi.

In doing so, Ferret can detect what hotspots the person has been through, giving an idea of their physical location; determine what e-mail servers or IM systems they attempt to access, lending an idea of their software and potentially their employer; and even scoop their IM contacts to determine who they communicate with.

"With seepage, we're talking about the distribution information that you actually mean to broadcast but which hackers can take and exploit for their own needs," Graham said. "All you have to do is turn on your computer and we can tell a lot about you."

For instance, computers made by Apple offer up details of what operating system someone is using when they turn their machines on or access Wi-Fi. If captured by a hacker, this could allow them to target specific malware attacks at the individual based on any known vulnerabilities in their version of the OS.