Biometrics Industry News

April 17, 2016

Biometrics and Anti-PassBack

The term anti pass-back is well known in the Time & Attendance and Access Control industry. Depending on what you use access control for, it can have many meanings. So in order to clarify the term and how it can work for you, lets deconstruct the phenomenon.

What is Anti-pass-back?

Broadly, the concept of Anti-pass-back can be viewed from three different angles:


Using token-based identification systems (cards, dongles, etc.), an employee is able to clock in through an access control system, and then pass his/her card back to one another person to use the same access token to gain entrance to a restricted area.  This makes the employer vulnerable to having unauthorised personnel on his/her premises. It can also cause confusion in HR and Payroll leading to overpaying of employees.


Conversely, having an employee sending his identification token to work with one of his colleagues, allows for the erroneous recording of working hours without having to physically show up for work.  Needless to state that this kind of pass-on behaviour has a direct impact on a company’s wage bill, as productivity figures and presenteeism statistics are almost impossible to rely on with 100% certainty.


Tailgating refers to an employee following another employee through a door, boom gate, or any other access controlled mechanism without presenting his credentials.  This can – to a large extent – be mitigated by the use of turn-stiles.  But even this is not fool-proof (ask the skinny guys).  If the necessity of providing credentials – be it token based or biometric – cannot be enforced, no system can prevent tailgating from occurring.  In this instance, the system as a whole fails, and it is therefore a point that should be mentioned, but excluded from further discussions in this writing.

The anti-anti-pass-back

To combat these kinds of fraudulent behaviour, various solutions have been developed around the following principles:

Traditional- ; Regional- ; Timed- ; and Nested Anti-pass-back control.

Traditional Anti-pass-back is a mechanism that simply relies on the alternative recording of In vs Out movement.  A person entering a parking lot must drive through the IN gate before being allowed to leave through the OUT gate.

Regional Anti-pass-back takes this one step further in that the rules build on one another to provide better logic and control through various regions.  A typical example of regional anti-pass-back is where a system disallows the entrance into a building if it was not preceded by an entrance onto the premises.

Timed anti-pass-back is a cost-saving solution where the system simply ‘forgets’ the status of a person after a given amount of time.  An example would be entrance into a work area where a person can re-enter the same door without having to clock OUT through another door, if, say 20 minutes, have elapsed since the previous clocking.

The last iteration of the anti-pass-back principle is that of Nested anti-pass-back where a designated sequence of entering/exiting certain doors is being enforced.  This is typically implemented in high-security areas where the actual predetermined sequence forms part of the security of the system as a whole.

So how is anti-pass-back enforced?

“Hard” anti-pass-back simply denies access when the predetermined anti-pass-back rules are not met.

“Soft” anti-pass-back has a more forgiving approach in that it allows access through the controlled area, but follows that with a notification to the administrator that the anti-pass-back rules have been violated.  It has been found that the “Soft” approach has the added benefit of not creating bottle-necks at high-usage areas like turn-stiles whilst hundreds of fellow employees try to enter the premises at the same time.  Consultative- and even disciplinary processes typically forms part of the “Soft” anti-pass-back implementation.

Does biometrics spell the end of anti-pass-back requirements?

If one precludes the principle of tail-gating, pass-back and pass-on behaviour, anti-pass-back in its traditional sense become irrelevant. It is physically impossible to clock through a device and then pass on ones fingerprint to another person to move through that same controlled point. The ievo fingerprint reader utilises the traditional principle of ‘in-out’ because the sequence of ‘in-in’ or ‘out-out’ will not work or will raises alarm bells to HR and payroll.

Not everyone uses anti-passback when they use the ievo entry system because it is just not necessary, the user simply wants the biometric as a form of security and nothing else. However, when it is being used, site administrators need to inform users that if they scan other people in or don’t scan out when they’ve already scanned in, they will find out by checking the fingerprint scanning logs. This can create problems on site and could also waste energy trying to find out the cause of problems and perpetrators.

If you are interested in a biometric door access system that allows for anti-passback, please contact us on 0845 643 6632 or visit our website

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