Although originally designed for use in manufacturing where larger amounts of data than can be encoded in a traditional single-dimensional barcode was needed, the versatility and amount of data storage that QR Codes allow for has expanded their capability and use greatly. The most common use is undoubtedly to link users to websites via phones capable of reading these codes, in particular smartphones. While any number of other uses exist, from loading contact information to providing access to wireless networks[1], the ability to launch hyperlinks is undoubtedly the most widespread use at least as far as the consumer market is concerned. This, however, can also be problematic as it carries all the same security concerns as clicking on a hyperlink from the web or, perhaps a better analogy as far as security is concerned, email.
Since many instances of QR Codes are found in public areas, they become vulnerable to attack via modification. Although several fairly complicated methods of modifying existing QR codes to do things other than what is intended exist[2], simply creating and attaching and new code seems the most likely and, despite the article's standpoint, easiest attack vector. Nonetheless, several interesting attacks are outlined that include several common url-based attacks such as SQL injection and command injection, as well as well as phone-specific attacks such as using a buffer overflow to compromise the phone or scanning device directly.[2]
Since QR Codes from a security standpoint can best be likened to links found within email, many of the same threats exist. The two most common types of threats that exist within email that could easily be extended to QR Codes are drive-by downloads and phishing scams. Drive-by downloads simply involve sending the user to a site that automatically downloads and installs software, generally malware, to the user's computer or device. These are quite common in email and as mobile device malware continues to become more prevalent QR Codes seem a good candidate for delivery along with traditional email.
Phishing, on the other hand, involves trying to get a user to enter and submit personal information, usually through a website that is designed to mimic a legitimate website. This is often limited simply to email addresses which will undoubtedly be added to spam lists, but can extend as far as online login credential for banks or even account numbers or social security numbers. A perfect example of how a QR Code might be used in phishing would be to attach a fake QR Code to a bank website that directs the user to a clone of the site and captures their login credentials. The sophistication of phishing sites varies, but can range from simply submitting whatever form data you enter as-is to creating a man-in-the-middle site that verifies with the actual bank site that a username exists and even circumventing security measures, for example fetching the Site Key from Bank of America and displaying it on the fake site. Others still will progressively escalate the sensitivity of the data they try to steal by starting out just gaining login credentials, but then asking you to fill out more sensitive data to "verify your account" on subsequent pages.
Some basic security precautions that are recommended when using QR Codes include verifying what URL the code is trying to take you to before actually allowing your device to follow it, including checking the destination URL in the case of shorteners.[1] This of course is easier said than done as most users of QR Codes are after the efficiency that they provide and are unlikely to check these things, especially in the case of shortened URLs. Even in the case of traditional browsers where the URL for a link is generally shown somewhere within the chrome of the browser, users often don't bother looking as is evidenced by the success of malicious sites in general. Even when checking this, knowing how to detect potentially risky URLs is a bit of an art that few people possess. Another security tip requiring diligence on the part of both those generating the QR Codes and those using them is to include in the case of the former and look for in the case of the latter https in the url.[3] SSL is becoming increasingly widespread, breaking out of the traditional use for just logging into an account, as security awareness and concerns become more prevalent, but is still not as recognized or widespread as is probably necessary yet. Security in general required diligence on the part of both those creating and maintaining systems as well as those using them, so the human factor is always they key limitation in security. Creating awareness, however, is the best way to increase security for a better and safer computing experience.
[1] Narayanan, A. Sankara. "QR Codes and Security Solutions." International Journal of Computer Science and Telecommunications 3.7 (2012): 69-72. Print.
[2] Kieseberg, Peter et al. "QR Code Security." SBA Research, unkown year. Print.
[3] Cole, Eric. "URL Shorteners / QR Codes." OUCH! June 2013: 1-3. Print.