When spear phishing met mass phishing

Introduction

Bulk phishing email campaigns tend to target large audiences. They use catch-all wordings and simplistic formatting, and typos are not uncommon. Targeted attacks take greater effort, with attackers sending personalized messages that include personal details and might look more like something you’d get from your employer or a customer. Adopting that approach on a larger scale is a pricey endeavor. Yet, certain elements of spear phishing recently started to be used in regular mass phishing campaigns. This story looks at some real-life examples that illustrate the trend.

Spear phishing vs. mass phishing

Spear phishing is a type of attack that targets a specific individual or small group. Phishing emails like that feature information about the victim, and they tend to copy, both textually and visually, the style used by the company that they pretend to be from. They’re not easy to see for what they are: the attackers avoid errors in technical headers and don’t use email tools that could get them blocked, such as open email relays or bulletproof hosting services included in blocklists, such as DNS-based blocklist (DNSBL).

By contrast, mass phishing campaigns are designed for a large number of recipients: the messages are generalized in nature, they are not addressed to a specific user and do not feature the name of the addressee’s company or any other personalized details. Typos, mistakes and poor design are all common. Today’s AI-powered editing tools help attackers write better, but the text and formatting found in bulk email is still occasionally substandard. There is no structure to who gets targeted: attackers run their campaigns across entire databases of email addresses available to them. It’s a one-size-fits-all message inside: corporate discounts, security alerts from popular services, issues with signing in and the like.

Attacks evolving: real-life examples

Unlike other types of email phishing, spear phishing was never a tool for mass attacks. However, as we researched user requests in late 2023, we spotted an anomaly in how detections were distributed statistically. A lot of the emails that we found were impossible to pigeonhole as either targeted or mass-oriented. They boasted a quality design, personalized details of the targeted company and styling that imitated HR notifications. Still the campaigns were too aggressive and sent on too mass a scale to qualify as spear phishing.

An HR phishing email message: the body references the company, the recipient is addressed by their name, and the content is specialized enough so as to feel normal to a vigilant user

Besides, the message linked to a typical fake Outlook sign-in form. The form was not customized to reflect the target company’s style – a sure sign of bulk phishing.

The phishing sign-in form that opened when the user clicked the link in the email

Another similar campaign uses so-called ghost spoofing, a type of spoofing that adds a real corporate email address to the sender’s name, but does not hide or modify the actual domain. The technique sees increasing use in targeted attacks, but it’s overkill for mass phishing.

An HR phishing email message that uses ghost spoofing: the sender’s name contains the HR team’s email address, lending an air of authenticity to the email

As in the previous example, the phishing link in the email doesn’t have any unique features that a spear phishing link would. The sign-in form that opens contains no personalized details, while the design looks exactly like many other forms of this kind. It is hosted on an IPFS service like those often used in mass attacks.

The IPFS phishing sign-in form

Statistics

The number of mixed phishing emails, March-May, 2024 (download)

We detected a substantial increase in the number of those mixed attacks in March through May 2024. First and foremost, this is a sign that tools used by attackers are growing in complexity and sophistication. Today’s technology lowers the cost of launching personalized attacks at scale. AI-powered tools can style the email body as an official HR request, fix typos and create a clean design. We have also observed a proliferation of third-party spear phishing services. This calls for increased vigilance on the part of users and more robust corporate security infrastructure.

Takeaways

Attackers are increasingly adopting spear phishing methods and technology in their bulk phishing campaigns: emails they send are growing more personalized, and the range of their spoofing technologies and tactics is expanding. These are still mass email campaigns and as such present a potential threat. This calls for safeguards that keep up with the pace of advances in technology while combining sets of methods and services to combat each type of phishing.

To fend off email attacks that combine spear and mass phishing elements:

• Pay attention to the sender’s address and the actual email domain: in an official corporate email, these must match.
• If something smells phishy, ask the sender to clarify, but don’t just reply to the email: use a different communication channel.
• Hold regular awareness sessions for your team to educate them about email phishing.
• Use advanced security solutions that incorporate anti-spam filtering and protection.