Blog
/
Email
/
March 30, 2023

Email Security & Future Innovations: Educating Employees

As online attackers change to targeted and sophisticated attacks, Darktrace stresses the importance of protection and utilizing steady verification codes.
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.
Written by
Dan Fein
VP, Product
Default blog image
30
Mar 2023

In an escalating threat landscape with email as the primary target, IT teams need to move far beyond traditional methods of email security that haven’t evolved fast enough – they’re trained on historical attack data, so only catch what they’ve seen before. By design, they are permanently playing catch up to continually innovating attackers, taking an average of 13 days to recognize new attacks[1]

Phishing attacks are getting more targeted and sophisticated as attackers innovate in two key areas: delivery tactics, and social engineering. On the malware delivery side, attackers are increasingly ‘piggybacking’ off the legitimate infrastructure and reputations of services like SharePoint and OneDrive, as well as legitimate email accounts, to evade security tools. 

To evade the human on the other end of the email, attackers are tapping into new social engineering tactics, exploiting fear, uncertainty, and doubt (FUD) and evoking a sense of urgency as ever, but now have tools at their disposal to enable tailored and personalized social engineering at scale. 

With the help of tools such as ChatGPT, threat actors can leverage AI technologies to impersonate trusted organizations and contacts – including damaging business email compromises, realistic spear phishing, spoofing, and social engineering. In fact, Darktrace found that the average linguistic complexity of phishing emails has jumped by 17% since the release of ChatGPT.  

This is just one example of accelerating attack sophistication – lowering the barrier to entry and improving outcomes for attackers. It forms part of a wider trend of the attack landscape moving from low-sophistication, low-impact, and generic phishing tactics - a 'spray and pray' approach - to more targeted, sophisticated, and higher impact attacks that fall outside of the typical detection remit for any tool relying on rules and signatures. Generative AI and other technologies in the attackers' toolkit will soon enable the launch of these attacks at scale, and only being able to catch known threats that have been seen before will no longer be enough.

Figure 1: The progression of attacks and relative coverage of email security tools

In an escalating threat landscape with email as the primary target, the vast majority of email security tools haven't evolved fast enough – they’re trained on historical attack data, so only catch what they’ve seen before. They look to the past to try and predict the next attack, and are designed to catch today’s attacks tomorrow.

Organizations are increasingly moving towards AI systems, but not all AI is the same, and the application of that AI is crucial. IT and security teams need to move towards email security that is context-aware and leverages AI for deep behavioral analysis. And it’s a proven approach, successfully catching attacks that slip by other tools across thousands of organizations. And email security today needs to be more about just protecting the inbox. It needs to address not just malicious emails, but the full 360-degree view of a user across their email messages and accounts, as well as extended coverage where email bleeds into collaboration tools/SaaS. For many organizations, the question is not if they should upgrade their email security, but when – how much longer can they risk relying on email security that’s stuck looking to the past?  

The Email Security Industry: Playing Catch-Up

Gateways and ICES (Integrated Cloud Email Security) providers have something in common: they look to past attacks in order to try to predict the future. They often rely on previous threat intelligence and on assembling ‘deny-lists’ of known bad elements of emails already identified as malicious – these tools fail to meet the reality of the contemporary threat landscape. Some of these tools attempt to use AI to improve this flawed approach, looking not only for direct matches, but using "data augmentation" to try and find similar-looking emails. But this approach is still inherently blind to novel threats. 

These tools tend to be resource-intensive, requiring constant policy maintenance combined with the hand-to-hand combat of releasing held-but-legitimate emails and holding back malicious phishing emails. This burden of manually releasing individual emails typically falls on security teams, teams that are frequently small with multiple areas of responsibility. The solution is to deploy technology that autonomously stops the bad while allowing the good through, and adapts to changes in the organization – technology that actually fits the definition of ‘set and forget’.  

Becoming behavioral and context-aware  

There is a seismic shift underway in the industry, from “secure” email gateways to intelligent AI-driven thinking. The right approach is to understand the behaviors of end users – how each person uses their inbox and what constitutes ‘normal’ for each user – in order to detect what’s not normal. It makes use of context – how and when people communicate, and with who – to spot the unusual and to flag to the user when something doesn’t look quite right – and why. Basically, a system that understands you. Not past attacks.  

Darktrace has developed a fundamentally different approach to AI, one that doesn’t learn what’s dangerous from historical data but from a deep continuous understanding of each organization and their users. Only a complex understanding of the normal day-to-day behavior of each employee can accurately determine whether or not an email actually belongs in that recipient’s inbox. 

Whether it’s phishing, ransomware, invoice fraud, executive impersonation, or a novel technique, leveraging AI for behavioral analysis allows for faster decision-making – it doesn’t need to wait for a Patient Zero to contain a new attack because it can stop malicious threats on first encounter. This increased confidence in detection allows for more a precise response – targeted action to remove only the riskiest parts of an email, rather than taking a broad blanket response out of caution – in order to reduce risk with minimal disruption to the business. 

Returning to our attack spectrum, as the attack landscape moves increasingly towards highly sophisticated attacks that use novel or seemingly legitimate infrastructure to deliver malware and induce victims, it has never been more important to detect and issue an appropriate response to these high-impact and targeted attacks. 

Fig 2: How Darktrace combined with native email security to cover the full spectrum of attacks

Understanding you and a 360° view of the end user  

We know that modern email security isn’t limited to the inbox alone – it has to encompass a full understanding of a user’s normal behavior across email and beyond. Traditional email tools are focused solely on inbound email as the point of breach, which fails to protect against the potentially catastrophic damage caused by a successful email attack once an account has been compromised.    

Fig 3: A 360° understanding of a user reveals their digital touchpoints beyond Microsoft

In order to have complete context around what is normal for a user, it’s crucial to understand their activity within Microsoft 365, Google Workspace, Salesforce, Dropbox, and even their device on the network. Monitoring devices (as well as inboxes) for symptoms of infection is crucial to determining whether or not an email has been malicious, and if similar emails need to be withheld in the future. Combining with data from cloud apps enables a more holistic view of identity-based attacks. 

Understanding a user in the context of the whole organization – which also means network, cloud, and endpoint data – brings additional context to light to improve decision making, and connecting email security with external data on the attack surface can help proactively find malicious domains, so that defenses can be hardened before an attack is even launched.

Educating and Engaging Your Employees

Ultimately, it’s employees who interact with any given email. If organizations can successfully empower this user base, they will end up with a smarter workforce, fewer successful attacks, and a security team with more time on their hands for better, strategic work. 

The tools that succeed best will be those that can leverage AI to help employees become more security-conscious. While some emails are evidently malicious and should never enter an employee’s inbox, there is a significant grey area of emails that have potentially risky elements. The majority of security tools will either withhold these emails completely – even though they might be business critical – or let them through scot-free. But what if these grey-area emails could in fact be used as training opportunities?    

As opposed to phishing simulation vendors, behavioral AI can improve security awareness holistically throughout organizations by training users with a light touch via their own inboxes – bringing the end user into the loop to harden defenses.  

The new frontier of email security fights AI with AI, and organizations who lag behind might end up learning the hard way. Read on for our blog series about how these technologies can transform the employee experience, dynamize deployment, augment security teams and form part of an integrated defensive loop.    

[1] 13 days is the mean average of phishing payloads active in the wild between the response of Darktrace/Email compared to the earliest of 16 independent feeds submitted by other email security technologies.

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.
Written by
Dan Fein
VP, Product

Blog

/

/

August 5, 2026

Testing a Prompt injection Attack Against an Enterprise AI Agent

prompt injectionDefault blog imageDefault blog image

Key takeaways

  • Darktrace successfully detected and quarantined a prompt injection email before it could be processed by an enterprise AI agent.  
  • Prompt injection attacks increasingly rely on natural language rather than traditional malware, making behavioral analysis an important complement to signature-based detection.  
  • Organizations deploying AI agents should combine model guardrails with behavioral monitoring to reduce the risk of malicious instructions reaching enterprise systems.

How behavioral detection helps stop prompt injection attacks

A Darktrace customer running a Gemini AI agent in Google Cloud asked us two simple questions:

“If my agent can read inbound emails and access internal data, what stops an attacker from hiding malicious instructions in the message? Couldn’t the agent be tricked into deleting or exfiltrating sensitive data?”

The scenario centers on an indirect prompt injection attack, where malicious instructions are hidden inside content that an AI model later interprets as trusted input. The same weakness was exposed by  EchoLeak (CVE-2025-32711), a zero-click Microsoft 365 Copilot vulnerability enabled data exfiltration from a single well-crafted email..

This blog follows the Darktrace team’s investigation of the customer’s hypothesis and examines how the attack interacted with their existing security stack. The results highlight which defenses held, where gaps emerged, and how behavioral detection mattered more than guardrails. This investigation also demonstrates why behavioral detection is becoming increasingly important for AI security, as prompt injections often contain no traditional indicators of compromise.  

How do prompt injection attacks work?

Prompt injection works by carefully crafting the content and structure of the prompt to alter the LLM’s behavior or output in unintended ways. This can cause models to violate guardrails, generate harmful content or enable unauthorised access.

Prompt injection attack example

The well-known example, EchoLeak (CVE-2025-32711), was a zero-click vulnerability in Microsoft 365 Copilot that relied on a carefully crafted email containing hidden instructions that the AI system interpreted as commands rather than content, creating a pathway for unauthorized access to sensitive information without any user interaction.

While Darktrace / SECURE AI is designed to prevent agents from producing unintended outcomes, we wanted to see if we could catch and prevent this threat type earlier in the attack life-cycle, at the email security layer.

How we tested prompt injection attacks on an enterprise agent

Summary:

  1. Claude generated a prompt injection payload.  
  2. Hidden instructions were embedded in an email.  
  3. The email passed traditional validation checks.  
  4. Darktrace analyzed the language and sender behavior.  
  5. The email was quarantined before the AI agent could process it.

To test Darktrace / EMAIL against this attack class, we opened Claude, gave it the customer's context and problem statement (Gemini agent with inbox access, internal tool calls), told it we were validating Darktrace / EMAIL's detection of prompt injections, and asked for a test payload. See below:

Figure 1
Figure 2

Despite the guardrails supposedly built into the model, Claude surprisingly gave us the entire exploit in plaintext (albeit very basic), illegible to a human as the text was sent in white text (see Figure 1) but framed as an authoritative override for anything downstream reading the mail programmatically (i.e. the Gemini agent).

How Darktrace detected a prompt injection attack

We then sent the Claude-crafted email from a freemail address to the target recipient’s inbox. Despite the email containing no malicious payload, the freemail address having no malicious reputation, and the validation checks all passing, Darktrace  /EMAIL flagged the email as a 93/100 anomaly and moved it to junk, out of scope for the AI agent.

Figure 3: The test email sent with the hidden prompt injection
Figure 4: The email analysis in Darktrace / EMAIL 
Figure 5: Darktrace / EMAIL detection of malicious activity

The interesting part is what triggered the detection (see Figure 5)

  • Possible machine prompt content: text in the body detected as instructions written for a machine to execute, not for a human to read
  • Possible machine prompt content + basic suspicious correspondence: the same content, correlated with sender-side anomalies: freemail domain (yahoo[.]com), unknown correspondent, no prior mail history with the recipient, and suspicious references to payment information

Neither of those is a signature match. Nothing in the email was on a blacklist. There was no malware, no link and no attachment. Darktrace analyzed the context in which the email was delivered and flagged it as likely risky.  The anomalous language features and the context of the sender relative to the recipient's normal behavior, combined with the unusual hidden text (prompt) were enough for Darktrace / EMAIL to act on the risk.

Result: Darktrace / EMAIL autonomously junked the email, out of scope for any AI agent parsing the inbox.

Why behavioral security makes a difference detecting prompt injection attacks

Cyberattacks don't look like traditional exploits anymore. They now operate in natural language, not strictly code.

That breaks the traditional stack. AV, firewalls, static scanning and signature-based SEGs all assume a payload to inspect.  

A prompt injection has no payload. It's just an instruction, written in natural language, dressed up as anything the attacker wants: an invoice, an HR request, a calendar invite, some simple PowerPoint slides.

EchoLeak proved that hidden instructions can sit inside an email invisible to the user but fully readable by the LLM, and the LLM will follow them blindly.  

This test and GTG-1002 proved that the LLM itself can be socially engineered. Tell it you're an authorized tester and it will hand you the attack.

Rules and static classifiers can catch the obvious cases. But natural language has infinite variants, and the attack surface is the model's innate functionality to comply.  

The deeper problem here is intent: an LLM can't reliably tell whether an instruction in its context came from its developer, its user, or an attacker who slipped it into an email. To the LLM, everything reads as language and looks like a legitimate ask. This is why behavioural detection wins, as you become aware of intent when you look at the context of an interaction. Does this sender normally send this kind of message to this recipient? Does this prompt fit the user's normal pattern? Is this agent behaving the way this agent normally behaves?  

Intent can't be read off a single email, it emerges from behavioral context. Which is how Darktrace enables threat detection, through behavioral understanding.

Why enterprise AI security requires more than guardrails

Claude didn't roll over immediately… the first section of the response was a (slight) pushback, but then it wrote the payload anyway without having to ask twice.

Here the framing of the prompt did all the work. The “testing security capabilities” angle moved the model from refusal to unquestioned compliance to the user prompt.

This isn't the first time this has happened, of course. Anthropic disclosed in November 2025 that a Chinese state-sponsored group they tracked as GTG-1002 ran the first documented AI-orchestrated espionage campaign against ~30 targets by posing as employees of a legitimate cybersecurity firm doing authorised penetration testing.

The takeaway isn't that AI guardrails are ineffective. They raise the cost of low-effort attacks and remain an important first layer of defense. However, for most organizations today, they’re the only line of defense when deploying AI agents. If a prompt injection bypasses those controls, organizations still need a way to detect and stop malicious behavior elsewhere in the attack chain.

Attackers will continue to have working prompt injections easily and quickly. The question is what stops one when it lands in an inbox your agent is reading.

That's where behavioral detection comes in.

How Darktrace detects prompt injection attacks in emails

Two things Darktrace does that a model-level guardrail or static rules and signatures can't:

Natural language analysis at the email or prompt layer. The email is assessed on its own merits: is this content shaped like instructions for a machine, regardless of what the receiving agent decides to do about it?

Behavioral context around the language. An AI agent behaves like an extremely agreeable human, and it will go above and beyond to comply with the user’s request. That's exactly why you must consider the business context, such sender behaviour, mailing history, and organisational norms, as these matter even more when the recipient is an AI.

Darktrace has been perfecting behavioral anomaly detection for over a decade; the same self-learning approach that catches BEC and account takeover applies directly to prompt injection delivery. Our multi-layered AI stack extracts content from the message, builds behavioural understanding through social graphing and Pattern of Life analysis, and then combines natural language, topic, inducement, sender relationship and anomaly signals before deciding what action to take.  

This matters for prompt injection because the threat is not the plain language itself, but the intent behind the language that can cause an AI agent to respond in unexpected ways.

How to secure enterprise AI operations from prompt injection attacks

Email was the entry point in this case, but it is only one of many possible vectors.  

Anywhere an agent can retrieve information, an attacker can potentially introduce a prompt injection.

Emails, documents, SharePoint sites, web pages, knowledge bases, chat platforms, and third-party integrations all provide opportunities to influence an agent's behavior. Wherever an agent finds its orders, a prompt injection opportunity exists.

This is why securing AI requires more than blocking malicious inputs. Organizations also need visibility into how agents behave after consuming information from across their environment. If an agent begins accessing unexpected data, taking unusual actions, or operating outside its normal patterns, those behaviors may provide the strongest signal that something has gone wrong.

Effective AI security requires defense in depth: reducing the likelihood of malicious instructions reaching the agent while maintaining the ability to detect and investigate suspicious behavior if they do.

The challenge isn't protecting a single entry point. It's recognizing that, in an AI-powered environment, every source of information is also a potential source of influence.

Are you deploying autonomous agents across your enterprise and want to see this tested in your environment? Let's talk.

Continue reading
About the author
Carlo Loregian
Solutions Engineer

Blog

/

/

August 4, 2026

Extending AI Security Visibility with Darktrace and Microsoft Agent 365

microsoft darktrace integrationDefault blog imageDefault blog image

AI agents are rapidly becoming embedded in everyday business operations, helping employees automate workflows, access information, and accelerate decision-making. As organizations embrace agentic AI, security teams face a growing challenge: understanding how AI is being used, what agents can access, and where risk may emerge.

As agents take on more business-critical work, security teams often need to move across multiple portals to understand risks spanning identity, data, and threat activity. This fragmented view can make it difficult to assess an agent's overall risk posture and determine where attention is needed. Organizations need a way to bring these signals together without disrupting existing security investments or workflows.

Today, Darktrace is announcing an integration between Darktrace / SECURE AI and Microsoft Agent 365 that brings Darktrace's Adaptive AI-driven risk signals directly into the Microsoft 365 Admin Center. By extending the visibility and risk understanding provided by Darktrace / SECURE AI into the Microsoft ecosystem, organizations can gain a more unified understanding of AI agent risk across their environments.

As one of the first security companies to partner with Microsoft to contribute third-party risk signals to the Agent Registry, Darktrace is helping shape how organizations understand and manage AI agent risk.

Extending visibility into the Microsoft Agent 365 experience

Microsoft Agent 365 provides administrators with a centralized registry of AI agents operating within their environment. As organizations expand their use of AI agents, this centralized visibility becomes increasingly important for governance and oversight.

This new integration extends that visibility by allowing Darktrace-generated risk signals to be surfaced directly within the Microsoft Agent 365 experience. By combining Microsoft's agent management and security capabilities with Darktrace's AI-powered risk analysis, organizations gain greater awareness of potential security concerns associated with AI agents operating across their environments.

By integrating Darktrace telemetry into Agent 365, customers can:  

  • Surface Darktrace-detected risks and signals alongside Microsoft-native signals in a single interface
  • Identify potentially compromised or anomalous AI agents more quickly
  • Gain unified understanding of context and agent behavior  

This approach reinforces a single control plane for AI security while allowing organizations to continue leveraging existing investments across both platforms.  

Why unified visibility of AI agent risk signals matters

As AI adoption accelerates across Microsoft environments, organizations must manage new forms of behavior, access patterns, and risk. Security teams need more than inventories and permissions. They need visibility into how AI systems operate and how risk evolves over time.  

This integration addresses a critical gap: how to bring behavioral AI security insights into the same control plane as identity, access, and agent management.  

With Darktrace and Microsoft Agent 365 together, organizations benefit from:  

  • Unified visibility: A single pane of glass for understanding AI agent risk signals across Microsoft and Darktrace signals  
  • Faster detection of abnormal agent behavior: Darktrace's Adaptive AI highlights deviations that may not be captured by static controls  
  • Operational efficiency: Security teams can triage and prioritize risk signals without switching between systems
  • Stronger trust in AI deployments: Clear attribution, context, and investigation pathways improve confidence in AI agent usage

Extending Microsoft's AI security model, not replacing it

Securing AI requires a layered approach that combines governance, visibility, threat detection, and risk management. This integration is designed to complement Microsoft's security capabilities, not duplicate them.  

Through Darktrace / SECURE AI, Darktrace contributes:  

  • Identification of risk via advanced prompt analysis  
  • Behavioral anomaly detection across AI agents  
  • Cross-environment threat correlation  
  • Autonomous insight into emerging or unknown risks  

Microsoft provides:  

  • Centralized agent management
  • Identity and access governance
  • Native detection of risk signals and enforcement capabilities

Together, these capabilities create a more complete, layered approach to securing AI-driven enterprises. Organizations gain the governance and policy controls needed to manage AI adoption while benefiting from continuous visibility into how AI is used across the business.

Building the future of secure AI

As AI agents become more deeply embedded in business processes, organizations need more than inventories and static controls. They need to understand how AI is being used, how agents behave, and where risk is emerging across the enterprise.

Darktrace / SECURE AI delivers that understanding through continuous visibility into AI activity, helping security teams assess intent, identify behavioral drift, and uncover emerging risk across both human and agent-driven workflows. Powered by Adaptive AI, it provides the context needed to secure AI as it evolves.  

The integration with Microsoft Agent 365 extends those insights into the workflows organizations already use. Agent 365 provides a unified control plane for governing and securing AI agents, while Darktrace contributes complementary behavioral risk signals that can be surfaced within the Agent 365 experience. Together, they give customers broader context on agent activity and risk while preserving the value of their existing Microsoft and Darktrace investments.

As enterprises move from AI experimentation to AI-powered execution, Microsoft and Darktrace help bring together governance, compliance, behavioral understanding, and oversight in a unified approach to AI security. For organizations adopting Microsoft 365 E7, Darktrace / SECURE AI further strengthens that foundation by providing continuous visibility into AI activity, agent behavior, and emerging risk as AI adoption scales.

Continue reading
About the author
The Darktrace Community
Your data. Our AI.
Elevate your network security with Darktrace AI