top of page

Homograph Attacks in the Context of SMS and Phishing

In the modern digital world, the complexity and variety of cyber threats continue to evolve. One such threat that has gained considerable attention in recent years is the 'homograph attack'. Initially seen as a concern for web browsers and email communications, homograph attacks have since found a new frontier in SMS-based phishing, also known as 'smishing'. This article will delve into the nature of homograph attacks, their impact on SMS communications, and the ways to mitigate these threats.

What are Homograph Attacks?

Homograph attacks, also known as Internationalized Domain Name (IDN) homograph attacks, are a type of cybersecurity threat where an attacker leverages the visual similarity between different characters to deceive the victim. The term 'homograph' refers to words that appear alike but have different meanings or origins, and in this context, it relates to how different characters from various languages or scripts can appear indistinguishable on a digital platform.

For example, consider the domain names "bank.tld" and "post.tld". At first glance, they seem trustworthy. However, a homograph attack could replace the Latin 'a' in "bank.tld" or the 'o' in "post.tld" with Cyrillic characters that look identical to the untrained eye, creating visually identical but malicious websites.

Those examples just look the same but are not:

  • bаnk.tld (with Cyrillic "а")

  • pоst.tld (with Cyrillic "о")

Another very dangerous example would to replace characters in "" with their Cyrillic counterparts which gives us "https://wеb.whаtsар". Here, the "e", "a" and "p" characters are replaced with their Cyrillic equivalents.

Please note that this URL looks nearly identical to the original in most contexts, which is exactly how a homograph attack works. Be aware that this kind of manipulation is used maliciously to deceive users into thinking they are visiting a legitimate website when they are actually being directed to a potentially harmful one.

These attacks traditionally took place in the realm of web browsers, where an attacker would register a domain name that visually mimics a popular website using different, but visually similar, Unicode characters. The victim, seeing what appears to be a familiar and trustworthy URL, would unknowingly visit the malicious site, which often leads to phishing, malware download, or other forms of cyber exploitation.

Homograph Attacks and SMS Phishing

With the widespread use of smartphones and the increasing popularity of SMS communication, homograph attacks have found a new avenue in SMS phishing, or 'smishing'. In a typical smishing scenario, an attacker sends a text message that appears to be from a trustworthy source, such as a bank or a known contact. The message often includes a link that, on the surface, seems to lead to a familiar website. However, the link is a homograph of the genuine URL, created by replacing some characters with visually similar alternatives from different scripts or Unicode character sets.

When the victim clicks on the link, they are taken to a fraudulent site designed to collect sensitive data, such as login credentials or financial information. Since SMS messages are typically perceived as more personal and direct compared to emails, victims are more likely to trust the sender and click on the deceptive link, making smishing a highly effective tool for cybercriminals.

The Dangers of Homograph Attacks

The dangers posed by homograph attacks are manifold. Not only can they lead to data breaches and financial losses, but they also erode trust in digital communication channels. This is particularly concerning given our increasing reliance on these channels for everyday communication, business transactions, and service access.

In the context of SMS phishing, homograph attacks can lead to disastrous consequences. Unlike email services, many SMS apps don't have robust spam filters or phishing detectors. This means that smishing attempts are more likely to reach their intended victims, and homograph attacks can therefore be particularly effective.

Mitigating Homograph Attacks

Protection against homograph attacks involves both technical countermeasures and user awareness.

On the technical side, a great solution is the CodeB TOTP SMS app. This application has an inbuilt homograph filter that can identify and block messages containing homograph attacks, thus providing an extra layer of security for users.

Other browsers and email services have implemented solutions to detect and flag potential homograph attacks. These solutions typically involve comparing the URL characters against a list of similar-looking characters from different languages or scripts. However, these solutions have their limitations, particularly when the malicious URL uses characters from multiple scripts.

To enhance these technical measures, user awareness and vigilance are paramount. Users should avoid clicking on links from SMS messages, chat applications, or social media without verifying the legitimacy of the URL.

The CodeB TOTP SMS app is an excellent tool in this context. This app allows easy implementation of two-factor authentication (2FA) by capturing 2FA QR codes from popular services like Facebook, Amazon, Google, Microsoft, Dropbox, and more. Most importantly, the app stores the 2FA seeds in the mobile's secure storage vault, thereby ensuring the safety of your seeds even if your phone is lost or stolen. It supports various encryption standards like SHA1, SHA256, and SHA512, and allows generation of 2FA codes even in the absence of a cellular or data network​1​.

One of the significant advantages of the CodeB SMS app is its built-in homograph filter as it is designed to detect and block messages that contain homograph attacks, thereby providing an additional layer of security to the users. This feature is particularly useful in the context of SMS phishing, where the traditional protections against homograph attacks, such as those implemented in web browsers and email services, might not be effective.


Homograph attacks are a sophisticated form of cyber threat that exploit the visual similarity of characters across different scripts and languages. While initially a concern for web browsers and emails, these attacks have found a new frontier in SMS phishing, adding a dangerous tool to the arsenal of cybercriminals. However, solutions like the CodeB TOTP SMS app, with its homograph filter, offer promising defenses against this threat. Coupled with user awareness and vigilance, we can mitigate the risks posed by homograph attacks and continue to secure our digital communications.

Recent Posts

See All

SMS Authenticity Checks

As many of us may already know, SMS is plagued with numerous fraud vectors. Not only are users bombarded with unsolicited messages, but...

How to report phishing text messages

Spam is extremely annoying, but you can help slow them down Phishing text messages present a significant hazard to vulnerable members of...


Commenting has been turned off.
bottom of page