Malicious Images: What's a QR Code

Published: 2011-08-03
Last Updated: 2011-08-03 17:48:52 UTC
by Johannes Ullrich (Version: 1)
6 comment(s)

I just wrote a quick note about the Cisco warranty CD mixup. While writing that, it came to me that currently quite a few of our readers may be visiting Las Vegas for this summers security drink fest. Historically, this has been a time to play various pranks on the audience of these conferences. In the past, fake ATMs, odd wifi networks, weird BGP issues and other tricks were mentioned.

One thing to look out for this year may be QR codes. 25% of internet users are now apparently using mobile devices. Many of them have known vulnerabilities the owner didn't bother to patch yet. At Vegas this week, you may prefer using your mobile device via 3G networks to avoid the notoriously unsafe Wifi networks offered at these conferences.

But there is one problem with mobile devices: The keyboard typically stinks. In particular on cell phones. To help you with that, we have "QR" codes. QR codes are bar codes that encode text and are commonly understood by mobile devices. Take a picture of it, and an app will take you to the encoded URL. Sadly, most people are not all that good in encoding barcode, and have no idea what they are entering. Compare it to handing your phone to a "friend" and telling them to type for you.

These barcodes can link directly to browser exploits, or could include other malicious content to manipulate your phone. If you spot a malicious code, let us know ... most of the applications will tell you what URL they are going to open up before they actually load it (similar to some of the short code URLs).


Johannes B. Ullrich, Ph.D.
SANS Technology Institute

Keywords: images qr code
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