IEEE Technology and Society Magazine - June 2015 - 36

As depicted in Fig. 1, a typical BCI system consists
of three main components: an acquisition system, an
application, and a signal processing system, where
the signal processing system consists of feature extraction and decoding (translation) algorithm components.
The existing BCI open-development platforms typically
grant every application developer full control over all of
these components. For the purposes of discussion here,
we will assume an attacker has an access to all of these
resources. We next consider how an attacker uses these
resources to develop malicious applications.

Types of Attackers
In Fig. 2, two types of attackers are shown (as described
in the caption). We distinguish between these types based
on the way an attacker analyzes recorded neural signals.
The first type of attacker extracts users' private information by hijacking the legitimate components of a BCI
system. Such an attacker exploits for malicious purposes
those feature extraction and decoding algorithms that are
intended for the legitimate BCI applications.
The second type of attacker extracts users' private
information by adding or replacing the legitimate BCI
components. Such an attacker implements additional
feature extraction and decoding algorithms, and either
replaces or supplements the existing BCI components
with additional malicious code. As can be observed from
Fig. 2, the difference between the two attacker types is
only in the structure of the "brain malware" component.

Methods of Extracting Private Information
We consider scenarios where an attacker interacts with
users by presenting them with specific sets of stimuli,
and recording their responses to the presented stimuli.
In the current literature, there are several well-established methods of presenting stimuli to users:
■ Oddball paradigm - a technique where users are
asked to react to specific stimuli, referred to as
target stimuli, hidden as rare occurrences in a
sequence of more common, non-target stimuli [37].
■ Guilty knowledge test - a technique based on the
hypothesis that a familiar stimulus evokes a different
response when viewed in the context of similar, but
unfamiliar items [38].
■ Priming - a technique that uses an implicit memory
effect where one stimulus may have an influence on
a person's response to a later stimulus [39].
We assume an attacker can use any of these methods to facilitate extraction of private information. In
addition, an attacker can present malicious stimuli in
an overt (conscious) fashion, as well as in a subliminal
(unconscious) way, with subliminal stimulation defined
as the process of affecting people by visual or audio
stimuli of which they are completely unaware [40]. Ways

of achieve unawareness typically include reducing a
stimulus intensity or duration below the required level
of conscious awareness.

Examples of "Brain Malware" Information Misuse
Private information about BCIs users, extracted using
"brain malware," may be of interest to multiple parties,
those using it for greater good and potential improvement of the quality of human lives, but also to those
using it to increase their own (financial) gains, as well
as those using it simply to harm others. One can easily
imagine the following examples of concerning BCIs use:
Example 1: As exemplified in Farahaney's work [21],
an access to an individual's memories and emotional
responses might be used by police enforcement and
government agencies during criminal investigation, as
well as for crime and terrorism prevention.
Example 2: BCI-recorded neural signals may be used
in a variety of entertainment and relaxation applications. A person's emotional response and satisfaction/
annoyment level may, for example, be used to provide
better (more accurate) music and/or movie recommendations. Similarly, information about a person's activity
and anxiety levels may be used to tailor a more personalized training routine or a relaxation session.
Example 3: Personal information, extracted from neural
signals, could also be used for targeted advertisement,
where in addition to (or instead of) information about a
person's activities on the Internet, an advertiser/retailer
would have a real-time access to a person's level of interest, satisfaction, or frustration with the presented material.
Example 4: On the other end of the spectrum, however,
extracted information about a person's memories, prejudices, beliefs, or possible disorders could be used to manipulate a person or coerce her/him into doing something.
Example 5: Finally, extracted neural information
could also be used to cause physical or emotional harm
to a person. Examples of such actions have already
been observed in the literature. Denning et al. [35],
presented the case of individuals who placed flashing
animations on epilepsy support webpages, eliciting seizures in some patients with photosensitive epilepsy.

Need for a Coordinated Prevention Approach
Issues arising from inappropriate use of BCI technology
most likely do not pose a critical concern yet, considering their limited use outside of research communities.
However, existing and emerging privacy and security
threats may be viewed as an attack on human rights to
privacy and dignity [41]. Thus, they deserve immediate
attention and careful consideration.
We suggest that methods to prevent and mitigate BCIenabled privacy and security threats must be developed
now, in the early design phase. Doing so will allow us

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