syssec_red_book

10. Usable Security10.7 Example ProblemsA multitude of examples exist for this specific topic. However, the problemis best depicted by the previously mentioned incident that happened to MattHonan, a renowned author for the magazine Wired [212]. He fell victim to anattack that ultimately led to his Amazon, Apple, Google and Twitter accountbeing compromised, and his Apple devices (iPhone, iPad and MacBook) beingwiped. Interestingly, the only direct fault of the victim was his casual approachto backups, a fault shared by many users. The incident itself was possiblebecause the different accounts were chained together in some way or another.Some had alternate e-mail accounts as backup authentication, others showedthe last few digits of a credit card, while some were simply compromised bycalling support and asking for a password reset. Inconvenient as the incidentmay be, it clearly illustrates an example of unusable security along well-placedexamples for social engineering.10.7.1 AuthenticationAuthentication played a major role in the above attack. One security guidelineis not to use two vital e-mail accounts for a two-factor authentication. If oneshould get compromised, it is quite possible that the other will be lost as well.Instead, the backup e-mail should be used only once, or on a different system(e.g., SMS two factor authentication) altogether. From the user’s perspective,however, it makes sense to use the same e-mail over and over again. Noordinary user is able to create e-mail aliases as needed and remember themafterwards. The same is true for passwords. If the same password is usedon multiple platforms (e.g., Google, Facebook), it is easy to compromise bothonce the password is somehow derived. It is quite easy to depict the problem.Solving it, on the other hand, is a completely different story. The sensible thingwould be not to allow secondary e-mail accounts as user verification. To beeffective, however, such a guideline has to be enforced throughout differentplatforms, and that is something no one can guarantee. Alternatively, a newmethod could be devised that ensures that daisy-chaining accounts togetheris not possible, while users still have the possibility of retrieving their lost orforgotten credentials. This topic could serve as the foundation of a researchthesis.10.7.2 BackupPeople are constantly told how important it is to backup their data. But whohas terabytes of external storage lying around? And if so, how often does theordinary user bother to actually create a backup? The answer is certainly: "Notoften enough." Devising a safe, cheap but still usable form of backup would be78