Cialdini (2001) identifies six fundamental psychological principles:
reciprocation, consistency, social proof, liking, authority and scarcity. As these principles direct human behaviour, they effectively give rise to influence techniques that are being efficiently put to use by "compliance practitioners" to power their tactics. (The term "compliance practitioners"
is used by Dr. Cialdini to generally identify those people who try to make others comply with their wishes. Clearly, Social Engineers form a subset of this group).
1. Reciprocation. One of the basic principles of human society is that if someone gives something to someone else, then the right thing for the recipient to do, is to somehow return the favour. This stems from the reciprocal nature of human society and goes back to the formation of the first human groups. The members of those groups had to share food and skills in order to survive. These basic principles evolved into the interdependencies of modern societies. Clearly, the action of giving and then expecting something in return as well as the other way round, on average, characterises all humans. The ways that this principle can be exploited by Social Engineers are many and range from the basic to the really intricate. "Free" offers on the Internet are very common. Most of the time, offers such as screensavers or background images are given away with the sole intention of persuading the recipient to register an email address in order to receive the free offer. At its most innocent form this technique is used to build up an e-mailing list to be used for promotional material or, worse, to be sold to others for the same use. Apart from the resulting spam mail flooding one's inbox, this type of attack is not very dangerous security-wise and this is the reason behind its popularity and success. Through the use of free email services one can create an address and register as requested, only to abandon the address at a later stage when spam sent to it becomes a nuisance. However, the Social Engineer may introduce a new twist to this story by directing the offer to particular targets and instead of providing just a piece of well-meaning software, entice the Mark to install software that could perform a secondary spying function in addition to its advertised primary function.
The principle of Reciprocation can also be applied in the already discussed "Reverse SE" attacks. When the Social Engineer solves the problem that torments the Mark, the Mark feels indebted to the Social Engineer and grants the Social Engineer the requested favours.
In an even more subtle form of reciprocation, the Social Engineer may make an almost unreasonable request, knowing that it will not be granted. By then making a lighter and less unreasonable request, the
Social Engineer augments the odds of this second request being granted, compared to the situation where the second request was the only one being made. Although seemingly unreasonable, there is logic behind this sequence. It should be clear that the Social Engineer's target was to not have the first request granted. The first request was only made to predispose the Mark according to the Social Engineer's plan. When the first request is turned down, the fact that the Social Engineer continues with a less demanding request, constitutes a concession on the Social Engineer's part. The Mark then feels obliged to reciprocate with a concession of his/her own because of the natural tendency to co-operate in the bounds of our societal interaction. This is similar to soliciting for money. A rather high amount of money is first asked for, and after this request is turned down, a second, smaller amount of money is almost certainly guaranteed to end up in the solicitant's money bag.
2. Commitment and Consistency. It is a known psychological fact that people are mostly consistent within their words, beliefs, attitudes and actions. This is fueled both by the fact that consistency is a virtue valued by society as well as by the useful shortcuts it provides. These shortcuts make daily life easier in the sense that if one remains consistent with previous choices, the load of re-processing all the data in similar situations as they arise is avoided. One simply sticks to earlier decisions.
As far as commitment is concerned, one has to just examine the positive load that the word "committed" carries in everyday conversations. If someone is characterised as "committed", then that someone can implicitly be trusted, is considered to be a person who brings results, is highly dependable etc. (For reasons of clarity and to avoid misconception, another use of the word "committed" is to describe someone who has been admitted to a mental institution. According to Meriam-Webster Online dictionary (Meriam-Webster, 2004) the first two meanings of the verb "commit" are: "a: to put into charge or trust : entrust, b: to place in a prison or mental institution". Clearly for the purposes of Cialdini's argument, reference is made to the first of the two meanings).
The Social Engineer makes good use of this principle by subtly manipulating the Mark so that the Mark gradually finds him/herself in such a position that turning down the Social Engineer's request is not an option.
This entrapment is based solely on the Mark's previous conduct towards the Social Engineer. In order for the Mark to be consistent towards the Social Engineer, assuming that the Mark has already granted the Social Engineer's inconsequential small favours, the Mark must keep granting the Social Engineer favours that are being gradually built up over many phone calls and an extended period of time. Doing otherwise, will make the Mark look inconsistent with respect to prior behaviour. In this case, the driving force behind the Mark's obsession with consistency is not, so much, what the public reaction would be if the fact that the Mark is inconsistent was brought to light, but rather the fact that if the Mark turns down the Social Engineer's request, this would force the Mark to holistically re-evaluate his/her position and evolved relation with the Social Engineer, since first contact was made. Not only can this make the whole mental-shortcut-based-on-previous-experience structure collapse (Cialdini, 2001), but it really is not an option in the mind of the Mark, since the Mark has to put his/her weight behind previous choices in order to remain psychologically balanced.
This attitude is further enforced by the fact that when person A asks person B for a favour and B grants it, A becomes part of B's personal history of good deeds that contributes to self-esteem. B (who granted the favour) will have to like A from that point onwards because B has to justify his/her action by convincing him/herself that this was the right thing to do as A "is a really nice person". It should also be noted that at the time of the favour being granted, B does not have to like A in order to grant the favour, but other reasons may lead B to this decision. Another interesting point is that none of the above necessarily holds true for A. A does not need to like B to ask for the favour, neither B becomes likeable by A after the favour is granted. On the contrary, it is possible for A to develop a dislike for B in order to justify that it was not a favour being granted but that somehow, B being a worse person than A, was obliged to grant A's
request.
All that is required from the Social Engineer in order to "cash in" on such attitudes is careful planning. A commitment in the form of a promise on the part of the Mark (direct, implied or even suggested) may be called upon by the Social Engineer in order to "nudge" the Mark at times of hesitation ("Aaaah… but you promised!").
3. Social Proof. According to Cialdini (2001, p.100) "we determine what is correct by finding out what other people think is correct". In part, this principle has already been discussed under Conformity, above. SE techniques based on the principle of Social Proof are most influential on a Mark, under conditions of either a) uncertainty or b) similarity. In the first case, if the situation is so ambiguous that the Mark does not know what to do, providing information on the actions of others will most certainly turn the Mark in the same direction (see Conformity above). In the second case on the other hand, since people are more inclined to follow the lead of others, similar to them, the work of a Social Engineer can be significantly facilitated or significantly impeded.
In a direct attack, the Mark may hesitate in providing the Social Engineer with the requested information. This hesitation indicates uncertainty and the Social Engineer will provide such conformity-related information to the Mark, that the Mark will be nudged in the desired direction.
Indirectly, the Social Engineer may benefit by lax security that allows users (i.e. potential targets) to function haphazardly with respect to security measures. This is a regenerative process that is fuelled by similarity and leads to an increasingly insecure work environment as more and more users following the example of others before them, develop disrespect towards security measures. On the other hand, if the proper security policies and directives are applied and the correct incentives are given to workers in order to uphold security and be rewarded for it, the
regenerative effect due to similarity will become positive and lead to augmented security.
4. Liking. People tend to respond favourably to other people with whom they share some common interest, hobby, birthplace etc. This natural tendency of ordinary people to like and even to seek out others who are like themselves, arms the Social Engineer with a powerful tactic. That of undertaking the role of a persona that appears more likeable to the Mark by virtue of similarity.
Generalising, people prefer to respond positively to those who they know and like. It is thus imperative that a Social Engineer become "liked" by the potential Mark. Apart form similarity, the most obvious aspect of all, that of physical beauty, is probably the most important factor for which people like other people. Whether it is conditioning or natural selection, research has shown (Cialdini, 2001) that physical attractiveness has an immediate effect on others, who instantly like those blessed with it. More interestingly though, other qualities of attractive people are further enhanced by the mere fact that their possessors are attractive! Hence, an attractive person will most probably also be considered to be kinder, more intelligent, more talented and, of course, more trustworthy than he/she really is. As a result, attractive people can be more persuasive than others
Liking can be achieved by familiarity over repeated contact (this was also mentioned under Friendliness, above). Also, if the circumstances under which contact takes place are positive rather than negative, liking is much more certain to be achieved sooner than later.
In SE attacks, these techniques are used to boost the level of liking that the Mark holds for the attacking Social Engineer. In physical attacks, the external appearance of the attacker has a major part in the scenario played out and the success of the attack altogether. In attacks over the phone and the Internet, a deep, resounding voice (natural or filtered through the appropriate voice-changing device) can contribute to the
success of the attack. Additionally, "chatting-up" the Mark in order to establish some common points of reference on which to build a trust relationship can make or break a successful attack. Stretching out the contacts in time can also help a Social Engineer build a trust relationship over the phone with the Mark and use that trust build-up when the attack culminates.
5. Authority. It has already been discussed that a false appeal to authority is one of the preferred methods of operation in SE attacks. The reason that such an impersonation is successful, is based on the respect that the average person has for authority. Modern societies systematically employ practices to instill in their members that obedience to legitimate authorities constitutes correct conduct (Cialdini, 2001, ch.6). Furthermore, persons of authority are considered to normally possess high levels of knowledge, wisdom and power. Hence, a mental shortcut can be established by deferring the complexity and responsibility of decision to such persons.
This, in effect constitutes an automatic response to persons of authority.
Alarmingly, though, as it is also discussed in the above reference, this automatic response tends to be to the symbols of authority and not necessarily to its credential-backed substance. Such symbols have been shown by research (Cialdini, 2001, p. 201) to be titles, clothing and automobiles. These symbols, used by the Social Engineer and combined with the right attitude and composure, can effectively project a convincing, albeit false, image of authority that will evoke an automatic response from the targeted Mark. Moreover, due to the automatic nature of the response, the Mark tends to underestimate the effect of authority pressure on his/her behaviour, thus making the attack more difficult to identify and protect against.
6. Scarcity. According to this principle, a higher value is assigned to goods and services that become less available. As this happens, their apparent value increases and so does the appreciation of their quality. Additionally, it is argued that as things become less available, our freedoms are effectively curtailed in the sense that we are no longer able to acquire
them as we used to. Psychological Reactance theory dictates that the human response to loss of freedom is to desire them even more strongly (Cialdini, 2001, pp.208-218). Hence, something that becomes scarce also becomes more desirable. (In other words, we appreciate something when we lose it).
Although it is clear that the scarcity principle applies more to deception based on fraudulent on-line auctions, the same principle can be used to enhance the effect of many other types of SE attacks.
For example, in the case of the "well-meaning" e-banking employee who wakes up the Mark in the middle of the night to inform him/her that money is being transferred out of his/her account and subsequently makes a request for the Mark's password to block the transaction, an extra piece of information about how the Social Engineer is risking his/her position in the bank to help the Mark is also usually supplied. Apart from the sense of gratitude that the Social Engineer is trying to conjure, the element of scarcity of the supplied service is also indirectly invoked. The Mark realises that if he/she hesitates to give the requested information to the Social Engineer, the offer may be swiftly withdrawn because of the impending risk of job loss for the bank employee / Social Engineer. This scarcity element makes the quality and sincerity of the offer to appear higher, and thus provides the Mark with a mental shortcut and the Social Engineer with the information he/she is after.
In the case of "phishing" attacks over email, IRC etc, an offer valid "for a limited time only" or "for the first X replies received" may trick the Mark into thoughtlessly and impulsively submitting personal information that will be used to impersonate him/her during a later phase of the SE attack or, even worse, be used to directly gain access to a system.
The above techniques are e-variations on a very old theme. Marketers, politicians, advertisers, sales people and con artists have been using them for ages to convince their Marks to respond positively to their
suggestions. Amazingly, although these methods were identified and brought to light decades ago, they are still very successful and the fact that computer-age Social Engineers use them, is a testament to their effectiveness. The average computer user is thus very vulnerable and the only means of defense is proactive education and distribution of information relevant to these methods of attack.