Security pictures are being used in a multitude of web applications to apply an extra step in securing the login process. However, are these security pictures being used properly? Could the use of security pictures actually aid hackers? Such questions passed through my mind when testing an application’s login process that relied on security pictures to provide an extra layer of security.
I was performing a business logic assessment for an insurance application that used security pictures as part of its login process, but something seemed off. The first step was to enter your username; if the username was found in the database then you would be presented with your security picture e.g. a dog, cat, iguana. If the username was not in the database then a message saying that you haven’t setup your security picture yet was displayed. Besides the clear potential for a brute force attack on usernames, there was another vulnerability hiding – you could view other users’ security pictures just by guessing the usernames in the first step.
Before I started to dwell into how should I classify the possible vulnerability in my assessment, I had to do some quick research in a couple of topics: what are security pictures used for? And, how do other applications use them effectively?
I always wondered what extra security the picture added. How could a picture of an iguana I chose protect me from danger at all? Or add an extra layer of security when I log in? Security pictures are mainly used to protect users from phishing attacks. For example, if an attacker tries to reproduce a banking login screen, a target user who is accustomed to see an iguana picture before entering his or her password would pause for a moment, then notice that something is not right since Iggy isn’t there anymore. The absence of a security picture produces that mental pause causing the user in most cases to not enter their password.
After finding about the true purpose of security pictures, I had to see how other applications use them in a less broken way. So I visited my bank’s website, entered my username, but instead of having my security picture displayed right away I was asked to answer my security question. Once the secret answer was entered my security picture would be displayed on top of the password input field. This approach to use a security picture was secure.
What seemed off in the beginning was the fact that because attackers can get users security pictures with a brute force attack, they can go a step further into phishing and use the security pictures of target users to create an even stronger phishing attack. This enhanced phishing attack would reassure the victim that they are in the right website because their security picture is there as usual.
Now that is clear that the finding was indeed a vulnerability, I had to think about how to classify it and what score to award. I classified it as Abuse of Functionality since WhiteHat Security defines Abuse of Functionality as:
“Abuse of Functionality is an attack technique that uses a web site’s own features and functionality to attack itself or others. Abuse of Functionality can be described as the abuse of an application’s intended functionality to perform an undesirable outcome. These attacks have varied results such as consuming resources, circumventing access controls, or leaking information. The potential and level of abuse will vary from web site to web site and application to application. Abuse of functionality attacks are often a combination of other attack types and/or utilize other attack vectors.”
In this case an attacker could use the application’s own authentication functionality to attack other users by combining the results of a brute force attack and the security pictures to create a powerful phishing attack. For the scores I have chosen to use Impact and Likelihood, which are given low, medium, and high values. Impact determines the potential damage a vulnerability inflicts and Likelihood estimates how likely it is for the vulnerability to be exploited. In terms of Likelihood, I would rate this a medium because it is very time consuming to setup a phishing attack and you will have to perform a brute force attack first to obtain valid usernames, then pick from the usernames the specific victims to attack; As for Impact, I would categorize this as high because once the phishing attack is sent the victim would most likely lose his or her credentials.
Security pictures can indeed help you add an extra layer of security to your application’s login process. However, put on your black hat for a moment and think how could a hacker use your own security against the application? As presented here, sometimes the medicine can be worse than the disease.