Spoofs, Subversion & Suspicion

Alternative titles:

Lazarick’s Liveness Lingo

Twisted Terminology Taxonomy

Voluntary Vocabulary Vexations
Where to start?

• This terminology is intertwined, so please be 

patient (i.e. don’t stone the messenger)

• Let’s start with some familiar examples, and 

look at their grouping titles

• Then we clarify between ‘Subversive’ and 

‘Suspicious’

• Some other familiar terms

• Lest we forget about testing terms
Table 1 Examples of Artificial and Human 

Subversive Presentation Characteristic Types

Artificial

Complete

artefact

gummy finger, latex finger, photo of face, photo of iris,

recording of voice, video of face, artificial hand, custom contact

lens, artificial/patterned contact lens, facial mask (ski,

theatrical, Halloween), opaque or theatrical contact lenses

Partial

artefact glue on finger,

sunglasses

false facial hair, cosmetics, removable implants,

Human

Lifeless cadaver part, severed finger/hand

Altered nose job, face lift, amputation, mutilation, 

fingerprints between hands and/or toes

surgical switching of

Non- Conformant

voice mimicry, hand shape control, forged signature, 

expression/extreme, tip or side of finger, falsetto voice

facial

Conformant zero effort imposter attempt

Coerced unconscious, under duress, drugged

subversive presentation 

presentation of an artefact or human characteristic to the biometric capture subsystem with the intent to interfere with or undermine the correct or 

intended policy of the biometric system.

artefact

artificial object(s) or characteristic(s) presenting a copy of biometric characteristics or synthetic pattern made to be presented to a biometric capture 

device with the aim of subverting the biometric system.
Some presentations can be Suspicious without being 

Subversive (top)

Some presentations can be Subversive, but not be 

detectable as being Suspicious (bottom)

SUBVERSIVE

Zero-effort imposter attempt (intending to defeat the system – by chance)

Coercion (with conformant presentation)

SUSPICIOUS

Artificial (patterned contact lens – cosmetic only {no mal-intent})

Altered (accidental scar/burn,...)

Non-conformant (poor training, not attentive, careless)

Artificial (with intent to defeat)

Lifeless

Altered (with intent to defeat)

Non-conformant (with intent to defeat)

Coercion (specific, detectable non-conformant)

NON-SUBVERSIVE – Good faith genuine presentation

Undetectable as Suspicious

Suspicious – from the 

capture system’s viewpoint

Subversive – from the test 

designer’s viewpoint

These security 

problems are 

detectable
It depends on your perspective...

Suspicious presentation detection (SPD) is the 

most comprehensive term (rather than 

artefact or liveness detection which are more 

commonly used). This takes the biometric 

capture system perspective.

Subversive presentation represents the test 

designer’s perspective, when the intent of the 

presentation is to defeat the system.
What about “spoof” and “liveness”?

Using the prior structure avoids dependence on 

these 2 terms, and their related “baggage”

For the record (WD3 includes): 

• spoof - in the context of biometrics, to make a 

subversive presentation (with conscious effort).

• liveness - the quality or state of being alive, made 

evident by anatomical characteristics (e.g. skin or 

blood absorption of illumination), involuntary 

reactions or physiological functions (e.g. iris 

reaction to light, heart activity – pulse), or 

voluntary reactions or subject behaviors (e.g. 

squeezing together fingers in hand geometry or 

response to a directive cue).
Liveness detection

• liveness detection - detection of anatomical characteristics 

or involuntary or voluntary reactions, in order to determine 

if a biometric sample is being captured from a living subject 

present at the point of capture.

{Note that liveness detection applies only to “lifeless” and in some 

instances “complete artefact” detection, but not other Suspicious 

Presentations}

SUBVERSIVE

Zero-effort imposter attempt (intending to defeat the system – by chance)

Coercion (with conformant presentation)

SUSPICIOUS

Artificial (patterned contact lens – cosmetic only {no mal-intent})

Altered (accidental scar/burn,...)

Non-conformant (poor training, not attentive, careless)

Artificial (with intent to defeat)

Lifeless

Altered (with intent to defeat)

Non-conformant (with intent to defeat)

Coercion (specific, detectable non-conformant)

Liveness 

only applies 

to these.
Additional (but secondary) Concept

What is the role/purpose of the attacker?

• Impersonator (synonym = impostor)

– “subversive biometric capture subject who attempts to be 

matched to someone else’s biometric reference.” [From 

ISO/IEC CD 2382.37] 

• Identity Concealer

– “subversive biometric capture subject who attempts to 

avoid being matched to their own biometric reference.” 

[From ISO/IEC CD 2382.37]
Overall testing metric terms

Performance metrics

Successful cases:

• True suspicious Presentation Detection Rate (TSPDR): the 

proportion of subversive presentations correctly classified as being 

suspicious 

• True Non-suspicious Presentation Detection Rate (TNSPDR): the 

proportion of non-subversive presentations correctly classified as 

being non-suspicious

Error cases:

• False Non-suspicious Presentation Detection Rate (FNSPDR): the 

proportion of subversive presentations incorrectly classified as 

being non-suspicious

• False suspicious Presentation Detection Rate (FSPDR): the 

proportion of non-subversive presentations incorrectly classified as 

being suspicious

Other more specific metrics also in WD3