Expanding Continuous Authentication with Mobile Devices


In our personal lives, we use several senses to identify or “authenticate” others: sight, hearing, and touch all play a role in recognizing someone, and we’re flexible enough that if only some of our senses detect an individual’s familiar characteristics, we still feel confident about that person’s identity. Furthermore, we draw on several aspects of each sense. For example, on the phone, we often recognize not only language and tone, but also intonation, diction, and other audible aspects that make the person on the other end identifiable to us. Even if it’s been years since we last saw or spoke with someone, our senses usually help us recognize them. We can decide how certain we are of their identity—saying hello doesn’t require the samelevel of trust as providing our Facebook login information.
Unlike humans, today’s computer systems don’t have the ability to recognize people. In early computing, most security was through physical access control such as a locked door. Authentication’s initial purpose was to track who was being charged for storage and computing time. However, the security environment has changed. Most computer access today permits sophisticated access control to one or more systems transparently, often relying on strong user authentication at the beginning of the session. This is a static mode of authentication; it’s typically performed using a token such as a password, smart card, or bio-metric, or a combination of these methods to allow access to the information or services.
Although we have strong static authentication mechanisms,the interconnection of multiple systems makes the protection and management of data more important than ever. Strong authentication systems aren’t useful less access is vigilantly protected. One concern with access control is when a user leaves the computer interface without logging off, or user abandonment. Simple methods of detecting user abandonment can create almost as many problems for the user as they solve. More sophisticated methods of detecting user interaction are needed for better security and usability

 

ABANDONMENT ISSUES

Ideally, once a computer has authenticated a user, it becomes the user’s responsibility to protect access to the computer’s data. This is usually ensured by maintaining control over the user interface—no one else has access to that session. However, users can be forgetful or assume that no one else would use the computer while theyrun a quick errand. This problem is pervasive enough that system administrators usually enforce some form of user abandonment detection to prevent unauthorized access.
A common method of detecting user abandonment is to monitor the input devices. When there’s no user interaction after a preset time, the user is logged off either directly or through a screen saver. Although this method works well for many users, it can be frustrating if a user is reading, giving a presentation, or otherwise passively engaging with the computer. The prompt for the user to re-authenticate could distract the user (and others) or interfere with the user’s work. This method also carries the risk of the user’s authentication token being compromised if the authentication occurs in a public setting, such as a conference.
Unfortunately, monitoring for activity doesn’t determine whether a different user accesses the computer. Walking away for a moment leaves plenty of time for another user to take over the session. The new user has the same rights as the individual who logged in, including sending, deleting, and changing information. This is often easily accomplished without the original user’s knowledge.

Developing stronger methods of authentication and tighter policies doesn’t necessarily help the user maintain control. For example, smart card policies often require that an authenticated smart card remain in the card reader, tying the user to the system.

However, in practice, the user is apt to walk away and leave the smart card in the card reader. Because the smart card might also be used for building access, the user could leave the area and not realize the smart card is missing until trying to return, leaving the computer accessible to others in the area. Other policies could result in constraining the user to one device at a time. Although most office workers might not have a problem with this policy, those working in a lab environment often operate multiple machines simultaneously.

           Chamodhi Weerasooriya
CIS 2011/2012

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