How QR codes work and what makes them dangerous – A computer scientist explains


Among the many many adjustments caused by the pandemic is the widespread use of QR codes, graphical representations of digital information that may be printed and later scanned by a smartphone or different machine, however there are some safety dangers. The Federal Trade Commission warned again in December 2023 in regards to the hazard of scanning a code from an unknown supply.

QR codes have a wide range of uses that assist folks keep away from contact with objects and shut interactions with different folks, together with for sharing restaurant menus, e-mail record sign-ups, automobile and residential gross sales data, and checking out and in of medical {and professional} appointments.

QR codes are a detailed cousin of the bar codes on product packaging that cashiers scan with infrared scanners to let the checkout pc know what merchandise are being bought.

Bar codes retailer data alongside one axis, horizontally. QR codes retailer data in each vertical and horizontal axes, which permits them to carry considerably extra information. That further quantity of knowledge is what makes QR codes so versatile.

Anatomy of a QR code

Whereas it’s simple for folks to learn Arabic numerals, it’s exhausting for a pc. Bar codes encode alphanumeric information as a sequence of black and white traces of assorted widths. On the retailer, bar codes file the set of numbers that specify a product’s ID. Critically, information saved in bar codes is redundant. Even when a part of the bar code is destroyed or obscured, it’s nonetheless potential for a tool to learn the product ID.

QR codes are designed to be scanned utilizing a digital camera, reminiscent of these discovered in your smartphone. QR code scanning is constructed into many digital camera apps for Android and iOS. QR codes are most frequently used to retailer internet hyperlinks; nevertheless, they will retailer arbitrary information, reminiscent of textual content or pictures.

Whenever you scan a QR code, the QR reader in your telephone’s digital camera deciphers the code, and the ensuing data triggers an motion in your telephone. If the QR code holds a URL, your telephone will current you with the URL. Faucet it, and your telephone’s default browser will open the webpage.

QR codes are composed of a number of elements: information, place markers, quiet zone and non-obligatory logos.

a black-and-white pattern with four numerical markers attached to arrows pointing to portions of the pattern
The QR code anatomy: information (1), place markers (2), quiet zone (3) and non-obligatory logos (4). Scott Ruoti, CC BY-ND
The information in a QR code is a sequence of dots in a sq. grid. Every dot represents a one and every clean a zero in binary code, and the patterns encode units of numbers, letters or each, together with URLs. At its smallest this grid is 21 rows by 21 columns, and at its largest it’s 177 rows by 177 columns. Usually, QR codes use black squares on a white background, making the dots simple to tell apart. Nevertheless, this isn’t a strict requirement, and QR codes can use any coloration or form for the dots and background.

Place markers are squares positioned in a QR code’s top-left, top-right, and bottom-left corners. These markers let a smartphone digital camera or different machine orient the QR code when scanning it. QR codes are surrounded by clean house, the quiet zone, to assist the pc decide the place the QR code begins and ends. QR codes can embrace an non-obligatory emblem within the center.

Like barcodes, QR codes are designed with information redundancy. Even when as a lot as 30% of the QR code is destroyed or tough to learn, the data can still be recovered. In reality, logos will not be truly a part of the QR code; they cowl up a number of the QR code’s information. Nevertheless, because of the QR code’s redundancy, the info represented by these lacking dots will be recovered by wanting on the remaining seen dots.

Are QR codes harmful?

QR codes will not be inherently harmful. They’re merely a technique to retailer information. Nevertheless, simply as it may be hazardous to click links in emails, visiting URLs saved in QR codes may also be dangerous in a number of methods.

The QR code’s URL can take you to a phishing web site that tries to trick you into coming into your username or password for an additional web site. The URL might take you to a authentic web site and trick that web site into doing one thing dangerous, reminiscent of giving an attacker entry to your account. Whereas such an assault requires a flaw within the web site you’re visiting, such vulnerabilities are common on the internet. The URL can take you to a malicious web site that methods one other web site you’re logged into on the identical machine to take an unauthorized motion.

A malicious URL might open an utility in your machine and trigger it to take some motion. Possibly you’ve seen this conduct once you clicked a Zoom hyperlink, and the Zoom utility opened and robotically joined a gathering. Whereas such conduct is ordinarily benign, an attacker might use this to trick some apps into revealing your information.

It’s vital that once you open a hyperlink in a QR code, you make sure that the URL is protected and comes from a trusted supply. Simply because the QR code has a emblem you acknowledge doesn’t imply it’s best to click on on the URL it comprises.

There may be additionally a slight probability that the app used to scan the QR code might include a vulnerability that enables malicious QR codes to take over your device. This assault would succeed by simply scanning the QR code, even should you don’t click on the hyperlink saved in it. To keep away from this menace, it’s best to use trusted apps offered by the machine producer to scan QR codes and keep away from downloading customized QR code apps.

Article written by Scott Ruoti, Assistant Professor of Laptop Science, University of Tennessee

This text is republished from The Conversation below a Inventive Commons license. Learn the original article.

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