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August 10, 2022

Bytesize Security: A Guide to HTML Phishing Attachments

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10
Aug 2022
Darktrace guides you through the common signs of HTML phishing attachments, including common phishing emails, clever impersonations, fake webpages, and more.

Common phishing emails

One of the most common types of phishing email seen by the Darktrace SOC, involves the use of HTML attachments (Figure 1). These emails make use of an attachment to hide redirects to overtly malicious or suspicious domains. Some even impersonate legitimate web pages and send any entered or captured information back to the attacker's infrastructure once opened or filled out by the recipient. Indicators of these attempts can be identified from a few key patterns found across multiple emails.

Figure 1: An example of a suspicious HTML attachment containing dynamic content

A typical feature of these HTML attachments is the use of a generic-sounding filename that relates to the message's subject line, but with no specific information pertaining to the recipient or their line of business. These files almost always contain some form of Javascript code, as they often make use of external Javascript libraries to accomplish whatever goal is being pursued. For example, an attacker might use Javascript to convincingly impersonate a trustworthy website and trick the recipient into providing credentials or sensitive information, or they might use it to deploy malware and get a foothold on the device for further compromise once opened. This can be further identified by the presence of certain links in the HTML file itself (Figure 2).

Figure 2: The HTML file previously referenced contained multiple rare and suspicious links

Figure 2 above is an example of an HTML file containing multiple links with calls for .js files. This shows that the attachment contains Javascript and is making calls for external libraries for an undetermined purpose. 

Another common red flag is when the file contains links to common Product or Service images from domains wholly unrelated to those services, as seen below (Figure 3).

Figure 3: An example of an unusual .png call from a rare domain. The subsequent image called is for a company with no apparent relation to the hosting domain

The examples above imply an obvious (and poor) attempt by the HTML file to impersonate a Microsoft webpage, likely a fake login page set up for credential harvesting, as the ‘Microsoft’ logo is being pulled from a domain entirely unrelated to Microsoft or any common image-hosting service. 

Rather than impersonating a website directly in the file and loading resources from external sources, these HTML files will instead directly point toward a webpage that already contains these elements. This comes with its own set of pros and cons: by hosting their phishing page in a public setting, they are far more likely to be taken down, however it may be easier to appear legitimate than if they were to build it all out in the HTML file itself. 

The final routine element in these types of HTML phishing emails is the mechanism by which the attacker intends to receive any successfully scammed credentials or information. If the fake webpage is entirely contained in the HTML file, this often presents as a suspicious PHP link present in the file itself (Figure 4).

Figure 4: Phishing HTMLs often include links to rare domains with PHP destinations as an indication that it will engage in some form of HTTP POST communication

PHP calls suggest that some part of the webpage is intended to submit an HTTP POST or equivalent ‘submission’ call, often present in the ‘Login’ button in these scenarios. After the victim clicks this button, the webpage sends all the form-submission items to the endpoint hosting the PHP page, which is commonly an indicator of the webserver hosting the attacker infrastructure running the phishing attack.

If the HTML file redirects to an externally hosted phishing page, identical PHP links are often found in the source code of those pages (Figure 5). This serves the same function as sending any entered credentials back to the attacker.

Figure 5: The source-code of an external-hosted phishing page, showing calls for PHP pages hosted on alternate attacker infrastructure

The process of HTML attacks is so standardized that they are commonly released in the form of easily deployable phishing kits. These can be deployed on unsuspecting compromised webservers with little to no modification, resulting in virtually identical attacks being seen year-round. WordPress seems to be a prime target for hosting such attacks, with the site owners often becoming unsuspecting victims in propagating these phishing campaigns. An unfortunate side effect of these kits being readily available is that the attackers often don't bother to set any sort of access restrictions on their phishing servers once established, which can result in their entire setup being publicly viewable with a simple link modification. One example is seen below (Figure 6).

Figure 6: The parent directory of the website hosting a suspicious PHP page was fully accessible without restriction

In this incident, the website hosting the PHP link seen earlier had a publicly accessible parent directory structure, where both the PHP file above and an additional suspicious .txt file could be seen. This .txt file appears to be where any information submitted by victims ultimately ended up written to (Figure 7).

Figure 7: The TXT file in the parent directory above appeared to contain the login information that was likely submitted to the PHP page referred to in the initial HTML attachment

Figure 7 above presents the unusual risk of not only having the victims’ credentials at the disposal of the original attacker, but also potentially exposed to any malicious actor that can get creative with a web-crawler to identify key elements of the files used by these particular phishing kits. 

Fortunately, due to the standardized nature of these ready-made phishing kits, these types of attacks often conform to a series of common behaviors that Darktrace / EMAIL excels in identifying. Despite being a popular technique, it is extremely rare for attempts using this HTML attachment method to successfully get through a correct Darktrace / EMAIL  deployment. Overall, this means one less risk for the end user to worry about.

Inside the SOC
Darktrace cyber analysts are world-class experts in threat intelligence, threat hunting and incident response, and provide 24/7 SOC support to thousands of Darktrace customers around the globe. Inside the SOC is exclusively authored by these experts, providing analysis of cyber incidents and threat trends, based on real-world experience in the field.
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Connor Mooney
SOC Analyst
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March 19, 2025

Global Technology Provider Transforms Email Threat Detection with Darktrace

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At a glance

  • Within just one month of using Darktrace / EMAIL, the volume of suspicious emails requiring analyst attention dropped by 75%, saving analysts 45 hours per month on analysis and investigation.
  • By offloading most manual, repetitive tasks to Darktrace / EMAIL, the company’s skilled security analysts can focus on developing new capabilities and tackling more complex, rewarding projects.
  • Darktrace recently detected and blocked a highly sophisticated and personalized phishing email that spoofed a Microsoft SharePoint and Teams website and used advanced engineering to impersonate the school of an employee’s family member.
  • The transition from the incumbent solution to Darktrace / EMAIL was seamless and undetectable to the company’s vast of customers and partners, reinforcing the security organization’s role as a business enabler—protecting the company and reducing risk without adding friction.

Securing a complex, distributed business without disruption

The company remains at the forefront of technological innovation and transformation; however, its success and ambitions come with the challenges of managing a distributed global business—balancing digital advancements, existing technology investments, and evolving compliance requirements.

Optimizing a complex tech stack for scalable growth

The organization operates a diverse technology stack spanning Windows, Mac, Linux, and multiple cloud environments, creating a complex and challenging IT landscape. The company’s Chief Information Security Officer (CISO) emphasizes the need for efficiency and agility. “Our goal is to scale and deliver new capabilities without increasing headcount, ensuring that costs remain proportionate to growth.”

Balancing security, governance, and business agility

Committed to responsible practices, this industry leader prioritizes secure and trustworthy technology for its customers who rely on its solutions. “Balancing business agility with governance is a constant challenge," said the CISO. "There’s always a natural push and pull, which I believe is healthy—but achieving the right balance is delicate.”

Protecting critical workflows without impacting productivity

For the organization, email is much more than just a communication tool. “Email plays a critical role in our engineering workflows and is fundamental to how we build our products.” Because of this, the company is extremely cautious about implementing any solution that could introduce friction or disrupt productivity. “There is zero tolerance for disruption, which is why we take a deliberate and methodical approach when evaluating, selecting, and deploying our tools and solutions,” he said.  

More than a vendor: A security partner invested in success

To ensure an optimal security infrastructure, the enterprise security team regularly evaluates market technologies to their existing solutions. With the rapidly evolving threat landscape, the CISO said they “wanted to validate whether we still had best-in-class protection and the right controls in place to secure our organization. It was about assessing whether we could do better in our ongoing effort to fine-tuning our approach to achieve the best possible outcome.”

The team evaluated 15 different email security vendors based on the following criteria:

  1. Efficacy to detect threats
  2. Ability to integrate with existing tooling
  3. Ease of use
  4. A vendor’s approach to partnership  

They initially narrowed the list to five vendors, conducting demo sessions for deeper evaluations before selecting three finalists for a proof of value (POV). We analyzed actual malicious emails with each vendor to assess the accuracy of their detections, allowing for an objective comparison,” said the CISO. Through this rigorous process, the Darktrace / EMAIL security solution emerged as the best fit for their business. “Darktrace’s product performed well and showed a genuine commitment to partnering with us in the long-term to ensure our success.”

The team objectively understood where there were gaps across the different vendors, where they were strong, and where they could use improvement. “Based on the analysis, we knew that Darktrace / EMAIL could deliver as the data supported it, in our specific use cases.  

Partnership, integrity and respect

Throughout the evaluation process, the importance of partnership and mutual respect remained an essential factor to the CISO. “I wanted a company we could develop a long-term strategic partnership with, one that could extend far deeper than just email.” A key factor in choosing Darktrace was the commitment and engagement of its team at every level of the organization. “Darktrace showed integrity, patience and a genuine investment in building a strong relationship with my team.  That's why we're here today.”

“Together, we've delivered some fantastic outcomes”

For the organization, Darktrace / EMAIL has played a crucial role in reducing risk, empowering analysts, and enabling a lean, effective security strategy. “Together, we've delivered some fantastic outcomes,” said the CISO.  

Reducing risk. Empowering analysts

“Within that first month, we saw a 75% drop in suspicious emails that that required manual review, which reduced the time my team spent analyzing and investigating by 45 hours per month,” said the CISO. The security team values Darktrace / EMAIL not only for its ease of use but also for the time it frees up for more meaningful work. “Giving my team the opportunity to tackle complex challenges they enjoy and find more stimulating is important to me.” As they continue to fine-tune and optimize balance levels within Darktrace / EMAIL, he expects even greater efficiency gains in the coming months.

Maximizing protection while staying lean

It’s important for the security group to be proportionate with their spending, said the CISO. “It's all about what is enough security to enable the business. And that means, as our organization grows, it's important that we are as lean and as efficient as possible to deliver the best outcomes for the business.”  Embracing an AI-powered automated approach is an essential component to achieving that goal. By offloading most manual, repetitive tasks to Darktrace / EMAIL, the company’s skilled security analysts can focus on more strategic and proactive initiatives that enable the business.  

Protecting employees from advanced social engineering threats

Recently, Darktrace detected a malicious email targeting an employee, disguised as a spoofed Microsoft SharePoint and Teams website. What made this attack particularly sophisticated was its personalization — it impersonated the school where the employee’s family member attended. Unlike mass malicious emails sent to thousands of people, this was a highly targeted attack, leveraging advanced social engineering tactics to exploit connections within the education system and between family members.  

Protecting without disrupting

A seamless migration is often overlooked but is critical to success for any organization, said the CISO. With a wide ecosystem of partners, email is a highly visible, business-critical function for the organization — "any friction or downtime would have an immediate impact and could throttle the entire business,” he said. However, the transition from their previous solution to Darktrace / EMAIL was exceptionally smooth. “No one realized we changed providers because there was no disruption — no incidents at all. I cannot emphasize just how important that is when I'm trying to position our security organization as an enabling function for the business that protects and reduces risk without adding friction.”

A security partnership for the future

“To survive as a business over the next few years, adopting AI is no longer optional—it’s essential,” said the CISO. However, with the cybersecurity market becoming increasingly saturated, selecting the right solutions and vendors can be overwhelming. He stresses the importance of choosing strategic partners who not only deliver the outcomes you need, but also deeply understand your organization’s unique environment. “You’re only as strong as your partners. Technology innovation and the cybersecurity market are always changing.  At some point every solution will face a challenge—it’s inevitable. The differentiator will be how people respond when that happens.”  

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March 19, 2025

Survey findings: How is AI Impacting the SOC?

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There’s no question that AI is already impacting the SOC – augmenting, assisting, and filling the gaps left by staff and skills shortages. We surveyed over 1,500 cybersecurity professionals from around the world to uncover their attitudes to AI cybersecurity in 2025. Our findings revealed striking trends in how AI is changing the way security leaders think about hiring and SOC transformation. Download the full report for the big picture, available now.

Download the full report to explore these findings in depth

The AI-human conundrum

Let’s start with some context. As the cybersecurity sector has rapidly evolved to integrate AI into all elements of cyber defense, the pace of technological advancement is outstripping the development of necessary skills. Given the ongoing challenges in security operations, such as employee burnout, high turnover rates, and talent shortages, recruiting personnel to bridge these skills gaps remains an immense challenge in today’s landscape.

But here, our main findings on this topic seem to contradict each other.

There’s no question over the impact of AI-powered threats – nearly three-quarters (74%) agree that AI-powered threats now pose a significant challenge for their organization.  

When we look at how security leaders are defending against AI-powered threats, over 3 out of 5 (62%) see insufficient personnel to manage tools and alerts as the biggest barrier.  

Yet at the same time, increasing cyber security staff is at the bottom of the priority list for survey participants, with only 11% planning to increase cybersecurity staff in 2025 – less than in 2024. What 64% of stakeholders are committed to, however, is adding new AI-powered tools onto their existing security stacks.

With burnout pervasive, the talent deficit reaching a new peak, and growing numbers of companies unable to fill cybersecurity positions, it may be that stakeholders realize they simply cannot hire enough personnel to solve this problem, no matter how much they may want to. As a result, leaders are looking for methods beyond increasing staff to overcome security obstacles.

Meanwhile, the results show that defensive AI is becoming integral to the SOC as a means of augmenting understaffed teams.

How is AI plugging skills shortages in the SOC?

As explored in our recent white paper, the CISO’s Guide to Navigating the Cybersecurity Skills Shortage, 71% of organizations report unfilled cybersecurity positions, leading to the estimation that less than 10% of alerts are thoroughly vetted. In this scenario, AI has become an essential multiplier to relieve the burden on security teams.

95% of respondents agree that AI-powered solutions can significantly improve the speed and efficiency of their defenses. But how?

The area security leaders expect defensive AI to have the biggest impact is on improving threat detection, followed by autonomous response to threats and identifying exploitable vulnerabilities.

Interestingly, the areas that participants ranked less highly (reducing alert fatigue and running phishing simulation), are the tasks that AI already does well and can therefore be used already to relieve the burden of manual, repetitive work on the SOC.

Different perspectives from different sides of the SOC

CISOs and SecOps teams aren’t necessarily aligned on the AI defense question – while CISOs tend to see it as a strategic game-changer, SecOps teams on the front lines may be more sceptical, wary of its real-world reliability and integration into workflows.  

From the data, we see that while less than a quarter of execs doubt that AI-powered solutions will block and automatically respond to AI threats, about half of SecOps aren’t convinced. And only 17% of CISOs lack confidence in the ability of their teams to implement and use AI-powered solutions, whereas over 40% those in the team doubt their own ability to do so.

This gap feeds into the enthusiasm that executives share about adding AI-driven tools into the stack, while day-to-day users of the tools are more interested in improving security awareness training and improving cybersecurity tool integration.

Levels of AI understanding in the SOC

AI is only as powerful as the people who use it, and levels of AI expertise in the SOC can make or break its real-world impact. If security leaders want to unlock AI’s full potential, they must bridge the knowledge gap—ensuring teams understand not just the different types of AI, but where it can be applied for maximum value.

Only 42% of security professionals are confident that they fully understand all the types of AI in their organization’s security stack.

This data varies between job roles – executives report higher levels of understanding (60% say they know exactly which types of AI are being used) than participants in other roles. Despite having a working knowledge of using the tools day-to-day, SecOps practitioners were more likely to report having a “reasonable understanding” of the types of AI in use in their organization (42%).  

Whether this reflects a general confidence in executives rather than technical proficiency it’s hard to say, but it speaks to the importance of AI-human collaboration – introducing AI tools for cybersecurity to plug the gaps in human teams will only be effective if security professionals are supported with the correct education and training.  

Download the full report to explore these findings in depth

The full report for Darktrace’s State of AI Cybersecurity is out now. Download the paper to dig deeper into these trends, and see how results differ by industry, region, organization size, and job title.  

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