Messages containing links to malware-infected websites represent a serious threat. Despite the numerous user education efforts, people still click on suspicious links and attachments, and their motivations for clicking or not clicking remain hidden. We argue that knowing how people reason about their clicking behavior can help the defenders in devising more effective protection mechanisms. To this end, we report the results of two user studies where we sent to over 1600 university students an email or a Facebook message with a link from a non-existing person, claiming that the link leads to the pictures from the party last week. When clicked, the corresponding webpage showed the "access denied" message. We registered the click rates, and later sent to the participants a questionnaire that first assessed their security awareness, and then asked them about the reasons for their clicking behavior.

When addressed by first name, 56% of email and 38% of Facebook recipients clicked. When not addressed by first name, 20% of email and 42.5% of Facebook recipients clicked. Respondents of the survey reported high awareness of the fact that clicking on a link can have bad consequences (78%). However, statistical analysis showed that this was not connected to their reported clicking behavior. By far the most frequent reason for clicking was curiosity about the content of the pictures (34%), followed by the explanations that the content or context of the message fits the current life situation of the person (27%), such as actually having been at a party with unknown people last week. Moreover, 16% thought that they know the sender. The most frequent reason for not clicking was unknown sender (51%), followed by the explanation that the message does not fit the context of the user (36%).

Therefore, it should be possible to make virtually any person click on a link, as any person will be curious about something, or interested in some topic, or find the message plausible because they know the sender, or because it fits their expectations (context). Expecting from the users error-free decision making under these circumstances seems to be highly unrealistic, even if they are provided with effective awareness training.

Moreover, while sending employees fake spear phishing messages from spoofed colleagues and bosses may increase their security awareness, it is also quite likely to have negative consequences in an organization. People's work effectiveness may decrease, as they will have to be suspicious of practically every message they receive. This may also seriously hamper social relationships within the organization, promoting the atmosphere of distrust. Thus, organizations need to carefully assess all pros and cons of increasing security awareness against spear phishing. In the long run, relying on technical in-depth defense may be a better solution, and more research and evidence is needed to determine the feasible level of defense that the non-expert users are able to achieve through security education and training.