We’ve written time and again about how QR codes are used in phishing schemes. Our secure email gateway solution even includes technology to read these codes — not just from emails, but also from attachments — and check the embedded links. Yet, attackers haven’t given up on trying to send QR codes to their victims. Lately, we’ve increasingly seen them use ASCII art for this purpose — images composed of characters. This seems particularly ironic considering that phishers once tried to evade link scanning by hiding links in images, and now they’re trying to dodge image scanning by going back to text. But with a few twists.

The lost art of ASCII, and how attackers use it

It’s hard to believe today, but there was a time when computers couldn’t display graphics. Consequently, the very first computer images were constructed from text characters. Following the adoption of the standard in 1963, characters from the ASCII (American Standard Code for Information Interchange) set were used for this type of artwork to ensure that images looked the same across different computers. Over time, other text symbols (for example, from the extended Unicode set) began to be used to create images, but the name “ASCII graphics” remained the term used to describe this art form as a whole. There were serious artists working in this medium, the earliest websites were designed with ASCII art, and even the first computer pornography was rendered with text characters.

As image display technology evolved, ASCII art began to fall out of fashion. It saw a major resurgence in the 2000s during the heyday of email spam. Back then, spammers primarily used it because it allowed them to disguise blatant spam keywords that could trigger mail filters, while also placing less load on mail servers than images. Additionally, since many users paid for volume of internet traffic at the time, they often disabled image loading in their email clients. Naturally, at that time, we augmented our email security solutions with technology specifically designed to block ASCII art.

Now, ASCII art has been rediscovered — this time by those looking to bypass technology that recognizes QR codes within images.

What does ASCII art phishing look like?

Here’s a recent example. The pretext itself is pretty run-of-the-mill: someone has supposedly sent to victim a confidential document via DocuSign, but to open it the recipient needs to scan the QR code in the email to visit a website and enter corporate login credentials.

A QR code rendered with unicode characters. We’ve blurred out a portion of the code to prevent the malicious link from being scanned.

Admittedly, the code looks weird. This is primarily because it’s drawn piece-by-piece in pseudo-graphic elements, and even the gaps between the lines can be seen. In reality, there’s no actual image in the e-mail message code; the QR code looks something like this behind the scenes:

ASCII art inside the email code

As a result, link scanners can’t see the link, and image analysis tools can’t find the URL hidden inside the QR code, so the attackers assume the phishing email is going to reach the victim just fine. Spoiler alert: no, we haven’t forgotten how to block ASCII art.

Is a QR code in an email even normal?

In theory, there are situations where using a QR code makes sense. It’s a fairly convenient way to share contacts, a link to a mobile app, a map location, or a configuration. In other words, it works well whenever information needs to be delivered specifically to the recipient’s mobile device.

However, someone using a QR code to make you enter corporate credentials on a mobile device is an instant red flag. And when that QR code is generated with ASCII art, it’s clearly a phishing attempt or an effort to lure you to a malicious URL. This trick can only have one purpose — an attempt to bypass security controls.

How to stay safe?

To prevent phishing emails — whether containing ASCII art or not — from ever reaching employee inboxes, we recommend using a secure email gateway with advanced anti-phishing capabilities. As an additional layer of defense, install security solutions on all endpoints used to access the internet.

Additionally, we recommend regular security awareness training to educate employees on modern phishing tactics. Specifically, to explain that ASCII art in modern emails can be a telltale sign of an attempted phishing attack.

We’ve written time and again about phishing schemes where attackers exploit various legitimate servers to deliver emails. If they manage to hijack someone’s SharePoint server, they’ll use that; if not, they’ll settle for sending notifications through a free service like GetShared. However, Google’s vast ecosystem of services holds a special place in the hearts of scammers, and this time Google Tasks is the star of the show. As per usual, the main goal of this trick is to bypass email filters by piggybacking the rock-solid reputation of the middleman being exploited.

What phishing via Google Tasks looks like

The recipient gets a legitimate notification from an @google.com address with the message: “You have a new task”. Essentially, the attackers are trying to give the victim the impression that the company has started using Google’s task tracker, and as a result they need to immediately follow a link to fill out an employee verification form.

To deprive the recipient of any time to actually think about whether this is necessary, the task usually includes a tight deadline and is marked with high priority. Upon clicking the link within the task, the victim is presented with an URL leading to a form where they must enter their corporate credentials to “confirm their employee status”. These credentials, of course, are the ultimate goal of the phishing attack.

How to protect employee credentials from phishing

Of course, employees should be warned about the existence of this scheme — for instance, by sharing a link to our collection of posts on the red flags of phishing. But in reality, the issue isn’t with any one specific service — it’s about the overall cybersecurity culture within a company. Workflow processes need to be clearly defined so that every employee understands which tools the company actually uses and which it doesn’t. It might make sense to maintain a public corporate document listing authorized services and the people or departments responsible for them. This gives employees a way to verify if that invitation, task, or notification is the real deal. Additionally, it never hurts to remind everyone that corporate credentials should only be entered on internal corporate resources. To automate the training process and keep your team up to speed on modern cyberthreats, you can use a dedicated tool like the Kaspersky Automated Security Awareness Platform.

Beyond that, as usual, we recommend minimizing the number of potentially dangerous emails hitting employee inboxes by using a specialized mail gateway security solution. It’s also vital to equip all web-connected workstations with security software. Even if an attacker manages to trick an employee, the security product will block the attempt to visit the phishing site — preventing corporate credentials from leaking in the first place.