How Cybercriminals Use URL Obfuscation in Phishing Attacks

By: Gonipalli Bharath Vel Tech University, Chennai, India International Center for AI and Cyber Security Research and Innovations, Asia University, Taiwan, Gmail: gonipallibharath@gmail.com

Abstract:

Criminals successfully use phishing attacks as their primary cyber threat method because they continuously improve their deception schemes to bypass security systems. Attackers employ URL obfuscation as one of their main deceptive techniques to disguise their malicious websites through URL manipulation. Fraudsters modify illegal links to look genuine so they can divert victims to fake sites where they must provide access details and financial information or personal data. Through URL shortening and character encoding as well as homoglyph attacks and redirection methods cybercriminals can bypass technological security measures to exploit human gullibility. Organizations and individuals must learn to identify these attack methods because doing so improves their ability to protect themselves from phishing risks. This research covers primary URL obfuscation methods along with recommendations about user safety against such online attacks.

Introduction:

The method of phishing serves cybercriminals well because they choose to exploit human behavior instead of seeking technical weaknesses. The ruthless approach guides victims to think they are connecting with authentic organizations however they land on fraudulent websites that steal user data from them. The technique known as URL obfuscation represents one of the most dangerous and advanced methods for executing phishing attacks[1]. The attacker modifies the URL format to impersonate legitimate sites then directs users to fake websites targeted against their data. Cautious users who inspect website addresses first attempt to click on links fall victim to obfuscated URLs because these deceptions look convincing. Attackers take advantage of shortened URLs together with encoded URLs through domain spoofing and also conduct homoglyph attacks and invisible redirections to conceal their malicious objectives[2].

The ability to detect how cybercriminals modify URLs becomes vital because advanced phishing strategies aim at users and organizations. The potential risks of obfuscation URLs used for phishing can be significantly reduced with the support of vigilant monitoring, web browser security tools, and education about security. We dissect the most popular methods of URL obfuscate in this post and explain ways to stay away from them[3].

Common Techniques of URL Obfuscation:

Criminals on the internet employ many kinds of strategies to ensure that infected URLs appear authentic. Among the absolute most popular techniques are:

• URL Shortening: Capacity to shorten URLs is provided through URL shortening services including Bit.ly TinyURL and goo.gl which helps users create brief condensed links. URL shortening tools provide handy links which suit well for email messages and social media. The feature of URL shortening provides a way for cybercriminals to conceal harmful URLs[4]. Users lack the ability to verify the destination website because shortened URLs keep the actual link hidden. Because victims are unable to identify the destination of the hyperlink, they frequently inadvertently visit a fake website.

Example:

Legitimate URL: http://malicious-website.com/login.html

Shortened URL: http://bit.ly/3xYZabc

• Hexadecimal and Unicode Encoding: The attackers execute URL encoding by applying either hexadecimal (% encoding) or Unicode characters to conceal the original URL. Such URLs become unrecognizable to people but browsers keep working inside them. Users perceive legitimate websites through encoding but remain unaware about the actual web destinations which allows attackers to deceive people with trusted-looking sites[5].

Example:

Regular URL: http://example.com/login

Encoded URL: http://%65x%61mple.com/login

• Homoglyph (Lookalike Characters) Attacks: Homoglyph attacks take advantage of characters which appear equal but work as different symbols in reality. Cybercriminals replace URL letters with Unicode characters and does similar modifications using Cyrillic or Greek characters to replicate legitimate websites. People might not be aware that they’re clicking on a fraudulent website because the variance is nearly invisible with the naked eye[6].

Example:

Legitimate URL: www.paypal.com

Phishing URL: www.pаypal.com (the letter “а” is a Cyrillic character, not an English “a”)

• Subdomain Spoofing: Online attackers establish deceptive subdomains that fool visitors into believing the site is authentic. The method of modifying domain structures enables attackers to create fake websites that appear as part of authentic domains. While “bank.com” appears in the URL, the actual domain is “secure-login.xyz,” which belongs to the attacker[7].

Example:

Legitimate: https://bank.com/login

Phishing: https://bank.com.secure-login.xyz

• Open Redirect Abuse: The feature of open redirects on certain websites permits domain redirections to third-party external websites. Being able to abuse this functionality enables phishing link creators to generate authentic-looking links. People may be led to a malware domain even though they’re convinced they’ve been browsing on a reliable hyperlink[8].

Example: https://trusted-website.com/redirect?url=http://malicious-site.com

How to Protect Against URL Obfuscation Attacks:

• Review the destination website by floating your mouse pointer above the link before executing the click.
• Seamless URL exposure happens through websites such as Check Short URL which exposes the entire link that exists under shortened URLs.
• Users should check for two components: websites must use https:// connections and possess valid security certificates.
• Users should investigate links containing domains that differ from the expected website structure.
• When users browse websites their current browsers trigger warning notifications for any detected suspicious sites.
• MFA provides protection even if someone steals your login credentials by requiring two or more verification factors.

Conclusion:

URL obfuscation is a type of advanced phishing technique that governs the appearance of URLs so that it is difficult for the users to distinguish malicious URLs. As cybercrime evolves, security awareness by itself cannot work anymore. People and organizations must catch up with the latest obfuscation techniques and implement active protection like security education, browser shields, and multi-factor authentication. By understanding how phishing URLs work, users are able to identify and avoid such spoofing attacks, reducing the risk of data compromise and financial loss. Cyber threats are evolving, but being aware and watchful, we can stay ahead of the perpetrators. Think before you click!

References:

1. P. Zhang et al., “CrawlPhish: Large-scale Analysis of Client-side Cloaking Techniques in Phishing,” in 2021 IEEE Symposium on Security and Privacy (SP), May 2021, pp. 1109–1124. doi: 10.1109/SP40001.2021.00021.
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3. B. B. Gupta, K. Yadav, I. Razzak, K. Psannis, A. Castiglione, and X. Chang, “A novel approach for phishing URLs detection using lexical based machine learning in a real-time environment,” Comput. Commun., vol. 175, pp. 47–57, Jul. 2021, doi: 10.1016/j.comcom.2021.04.023.
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5. S. Ismail, M. H. Alkawaz, and A. E. Kumar, “Quick Response Code Validation and Phishing Detection Tool,” in 2021 IEEE 11th IEEE Symposium on Computer Applications & Industrial Electronics (ISCAIE), Apr. 2021, pp. 261–266. doi: 10.1109/ISCAIE51753.2021.9431807.
6. “AI-Driven Phishing Detection: Combating Cyber Threats Through Homoglyph Recognition and User Awareness | Proceedings of the 2024 The 6th World Symposium on Software Engineering (WSSE).” Accessed: Feb. 25, 2025. [Online]. Available: https://dl.acm.org/doi/abs/10.1145/3698062.3698095
7. R. Goenka, M. Chawla, and N. Tiwari, “A comprehensive survey of phishing: mediums, intended targets, attack and defence techniques and a novel taxonomy,” Int. J. Inf. Secur., vol. 23, no. 2, pp. 819–848, Apr. 2024, doi: 10.1007/s10207-023-00768-x.
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Cite As

Bharath G. (2025) How Cybercriminals Use URL Obfuscation in Phishing Attacks, Insights2Techinfo, pp.1

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