The failure of users to follow security advice has often
been noted. They chose weak passwords, ignore secu-
rity warnings, and are oblivious to certificates. It is
often suggested that users are hopelessly lazy and un-
motivated on security questions. We argue that users’
rejection of the security advice they receive is entirely
rational from an economic perspective. As with many
activities, online crime generates direct losses and ex-
ternalities. The advice offers to shield them from the
direct costs of attacks, but burdens them with the in-
direct costs, or externalities. Since the direct costs are
generally small relative to the indirect ones, they reject
this bargain. We examine three areas of user educa-
tion: password rules, phishing site identification, and
SSL certificates. In each we find that the advice is com-
plex and growing, but the benefit is largely speculative
or moot. In the cases where we can estimate benefit, it
emerges that the burden of following the security advice
is actually greater than the direct losses caused by the