Two studies. The first one looks at social phishing:
Test subjects received an e-mail with headers spoofed so that it appeared to originate from a member of the subject’s social network. The message body was comprised of the phrase “hey, check this out!” along with a link to a site ostensibly at Indiana University. The link, however, would direct browsers to www.whuffo.com, where they were asked to enter their Indiana username and password. Control subjects were sent the same message originating from a fictitious individual at the university.
The results were striking: apparently, if the friends of a typical college student are jumping off a cliff, the student would too. Even though the spoofed link directed browsers to an unfamiliar .com address, having it sent by a familiar name sent the success rate up from 16 percent in controls to over 70 percent in the experimental group. The response was quick, with the majority of successful phishes coming within the first 12 hours. Victims were also persistent; all responses received a busy server message, but many individuals continued to visit and supply credentials for hours (one individual made 80 attempts).
Females were about 10 percent more likely to be victims in the study, but male students were suckers for their female friends, being 15 percent more likely to respond to phishes from women than men. Education majors had the smallest disparity between experimental and control members, but that’s in part because those majors fell for the control phish half the time. Science majors had the largest disparity—there were no control victims, but the phish had an 80 percent success rate in the experimental group.
Okay, so no surprise there. But this is interesting research into how who we trust can be exploited. If the phisher knows a little bit about you, he can more effectively target your friends.
And we all know that some men are suckers for what women tell them.
Another study looked at the practice of using the last four digits of a credit-card number as an authenticator. Seems that people also trust those who know the first four digits of their credit-card number:
Jakobsson also found a problem related to the practice of credit card companies identifying users by the last four digits of their account numbers, which are random. From his research, it turns out people are willing to respond to fraudulent e-mails if the attacker correctly identifies the first four digits of their account numbers, even though the first four are not random and are based on who issued thecard.
“People think [the phrase] ‘starting with’ is just as good as ‘ending with,’ which of course is remarkable insight,” he said.
Another attack comes to mind. You can write a phishing e-mail that simply guesses the last four digits of someone’s credit-card number. You’ll only be right one in ten thousand times, but if you send enough e-mails that might be enough.
EDITED TO ADD (8/14): Math typo fixed.