Attackers aren’t just sending sketchy links anymore; they’re crafting subdomains that look almost identical to real websites, called phishing subdomains. It’s not just a trick; it’s a tactic designed to fool even the most cautious users. So the question is: how dangerous has phishing become? Let’s check out some stats to answer that.
According to CISA’s 2023 Phishing Campaign Assessment, 84% of employees respond to a malicious email within the first 10 minutes, either by sharing sensitive information or engaging with a fraudulent link or attachment.
Meanwhile, data from Statista shows that in Q4 2024, more than 989,000 distinct phishing attacks were identified globally, marking a slight increase compared to the previous quarter.
Understanding how phishing works is a must to protect yourself and others, so let’s take a deeper look at it and see the role of malicious phishing subdomains.
Table of Contents
What Is a Subdomain?
A subdomain is an extension of a main domain, used to organize or separate different parts of a website. For example, on the domain example.com, you might see subdomains like blog.example.com or store.example.com. These can act as separate websites while remaining tied to the primary domain. Subdomains are commonly used for segmenting content, hosting services, or creating distinct environments within the same brand.
So, where do phishing subdomains come in? To understand it, first, we need to know what is phishing exactly.
What Is Phishing?
Phishing happens when someone pretends to be a trusted source (a bank, a colleague, a service you use) just to steal your info. It could be through an email, a fake login page, or even a text message. The idea is simple: get you to let your guard down. Attackers often pose as banks, social networks, or online services via emails, text messages, or fraudulent websites. The end goal is usually identity theft or data theft.
IBM defines phishing as “a type of cyberattack that uses fraudulent emails, text messages, phone calls or websites to trick people into sharing sensitive data.”
How Subdomains Are Used in Phishing
What makes phishing subdomains so deceptive is how legitimate they can appear. Instead of registering a fake domain like fake-bank-login.com, attackers might go for something that looks more plausible, like login.fakebank.com. Worse yet, if they manage to exploit the DNS configuration of a legitimate domain, they could create subdomains like secure-login.bank.com, which can easily confuse users unfamiliar with how domains work.
This tactic gives attackers two major advantages:
- Increased credibility: A subdomain that includes a real brand name (even as part of a larger fake domain) can mislead users into thinking they’re on the official site.
- Visual deception: To untrained eyes, the differences between a legitimate URL and a phishing one may be subtle, especially if the fake page looks professional.
The Role of DNS Records
DNS (Domain Name System) records are the “phone book” of the Internet, translating human-readable domain names into IP addresses used by computers to locate servers. Two types of records are particularly relevant here:
- A Records: Map a domain or subdomain to an IPv4 address.
- CNAME Records: Point one domain to another as an alias.
When it comes to phishing subdomains, attackers configure these DNS records, either on a domain they control or, in more dangerous cases, on a compromised legitimate domain, to redirect victims to malicious servers. These servers host phishing pages crafted to mimic real websites and harvest credentials.
This type of attack often exploits what’s known as a security misconfiguration, for example, when a DNS record is left pointing to an outdated or abandoned service, or when access controls around domain or DNS management are too lax.
Real-World Examples
Let’s look at some real-world cases of phishing subdomains or related vulnerabilities that made it to the headlines.
Subdomains of Microsoft Vulnerable to Takeover: In 2020, researchers at Vullnerability.com (yes, with 2 Ls) discovered and claimed over 670 forgotten Microsoft subdomains, including seemingly trustworthy ones like data[.]teams[.]microsoft.com and identityhelp[.]microsoft.com. These abandoned assets could easily be converted into phishing subdomains and abused for phishing or malware campaigns, all while appearing legitimate to users. The root cause? Poor DNS hygiene and lax cloud subdomain management.
Vullnerability.com responsibly disclosed their findings, but the broader issue affects any company using cloud services, not just Microsoft.
Financial Domains Involved in Phishing: A research by BforeAI highlights a growing trend in phishing and spoofing targeting the financial sector. Between January and June 2024, 62,074 domains containing financial keywords were registered. Of those, about 62% were linked to phishing campaigns using spoofed websites to impersonate legitimate institutions.
BforeAI’s report points to the widespread availability of phishing kits as a key factor driving this increase. These tools make it easier for attackers to launch convincing scams with minimal technical effort. Additionally, deepfake technology is making it even simpler for bad guys to mimic real individuals or brands convincingly.
Detection and Prevention of Subdomain Phishing
Protecting against this kind of attack takes more than just good tools, it takes good habits, too. It requires both user education and strong domain management policies to prevent the creation of phishing subdomains.
For users:
- Check the full URL: Pay close attention to the domain name, not just the beginning or the padlock icon.
- Look for HTTPS, but don’t rely on it alone: While HTTPS indicates a secure connection, it doesn’t guarantee the site is trustworthy. Many phishing sites use valid SSL certificates.
- Avoid clicking suspicious links: Especially those received via unsolicited emails or messages asking for personal data.
- Manually type URLs: Enter the website address directly into your browser instead of clicking on email links.
For domain administrators:
- Monitor DNS activity: Use tools to detect unauthorized subdomain creation and also look for DNS misconfigurations.
- Restrict subdomain creation: Apply strict internal policies and change management processes around DNS modifications.
- Use DNSSEC: This technology helps validate DNS records and reduce the risk of DNS spoofing or tampering.
- Employee awareness: Educate staff about phishing risks and how to identify suspicious sites or DNS anomalies.
- Scan your website: While not directly related to DNS, by using our web security scanner, you can quickly scan your website to potentially detect dozens of dangerous misconfigurations.
Consequences
The impact of phishing via subdomains can be rough, and it isn’t just technical; it can be both personal and incredibly costly.
For Individuals
When someone unknowingly falls for a phishing scam, the consequences can be immediate and serious. Stolen login credentials or personal data can quickly lead to identity theft, unauthorized access to online accounts, or financial loss. In some cases, attackers use that information to drain bank accounts, open new credit lines, or sell the data to others.
Beyond the financial hit, there’s the emotional toll. Victims often feel embarrassed or violated, especially if the scam looked like it came from a company they trusted. That shaken trust can make people hesitant to engage with online services in the future, even legitimate ones.
For Organizations
For companies, the damage can spread even further. If customers get tricked by a phishing site that uses a subdomain resembling the company’s name, they may blame the organization, even if it wasn’t directly at fault. That loss of trust is hard to rebuild.
Reputation damage aside, the operational costs can pile up fast, especially if attackers gain access to internal systems or sensitive data. Recovering from a phishing incident often means paying for forensic investigations, legal support, customer notifications, and sometimes public relations cleanup.
And if regulators find that the company didn’t take enough steps to protect user data or monitor domain activity, there could be legal consequences, including hefty fines. For smaller businesses in particular, a well-executed phishing campaign can cause disruption that’s difficult to recover from, both financially and reputationally.
Summary
What makes phishing subdomains so dangerous isn’t just the tech, it’s the trust. If a link looks like it belongs to your bank or workplace, most people won’t think twice. That’s exactly what attackers are counting on. Staying ahead means more than looking for HTTPS; it’s about understanding how these attacks are built.
Both users and administrators must take proactive steps to stay ahead of these threats. Vigilance, education, and the right technical safeguards are the best defense against these kinds of attacks.