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December 13, 2023

Defending Against Personalized Cyber Attacks

Stay informed about the latest trends in cyber threats with Darktrace experts, including how attacks are evolving and becoming more personalized.
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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The Darktrace Community
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13
Dec 2023

Cyber-attacks are getting personal. The usual opportunistic “spray and pray” attacks that reach many would-be targets at once are still present, but as cyber defence has advanced, today’s more sophisticated campaigns take precise aim at a particular company.

Threat actors willingly put in extra time and effort to realize a bigger payday at the end of it, but developments in the tools they have at their disposal are also making targeted, personal attacks easier.

CAPTCHA-breaking AI techniques like computer vision and convolutional neural networks can be used to gather information on an organization’s attack surface, and Generative AI is able to perform OSINT collection on a specific target, or targets, within an organization. Once inside, attackers can further leverage AI to automatically tweak attacks and create novel, highly targeted threats that elude defenses.

A new white paper, The CISO’s Guide to Cyber AI, explains how CISOs and their teams can make smarter use of defensive AI and machine learning (ML) to protect today’s digital environments from these and more advanced novel threats.

Today’s threats don’t necessarily resemble past attacks  

Darktrace analytics pointed to a sharp rise in novel cyber-attacks earlier this year. Generative AI and large language model (LLM) tools continue to lower the barrier to entry for threat actors, making it easier than ever to build smarter, faster, more targeted attacks.

But while attacks are getting personal, security tools that apply AI in the wrong way won’t see these attacks coming.

Here’s why: most cyber security tools and platforms rely on a combination of supervised machine learning, deep learning, and transformers to train and inform their systems. This entails shipping your company’s data out to a large data lake housed somewhere in the cloud where it gets blended with attack data from thousands of other organizations. The resulting homogenized data set gets used to train AI systems — yours and everyone else’s — to recognize patterns of attack based on previously encountered threats.

At its conception, this was a reasonably smart way of approaching cyber security. For a long time, the assumption that today’s threats will resemble yesterday’s attacks was a valid one. But in an age where the commoditization of cyber-crime has lowered the bar-to-entry for attackers, and where Generative AI and other open-source tools are enabling personalized attacks at scale, this is no longer the case.

Darktrace has seen evidence this year of a marked rise in more sophisticated attack techniques. Between May and July this year, our Cyber AI Research Centre observed that multistage payload attacks, in which a malicious email encourages the recipient to follow a series of steps before delivering a payload or attempting to harvest sensitive information, have increased by an average of 59% across Darktrace customers. Some of this will be QR code phishing, the latest trend in attack tactics, others will include automation. The speed of these types of attacks will likely rise as greater automation and AI are adopted and applied by attackers.

This ‘historical’ approach is not able to identify threats that haven’t been seen before: attacks that use new malware, novel social engineering, and those that are targeted to your organization. There are no indicators of compromise (IoCs) to teach your system to recognize these kinds of attacks.

IoC-based defenses won’t necessarily spot strange and unusual activity by an authorized user, device, or known IP address until threat actors tip their hand — and by then it’s too late. Looking for repeat patterns works well for detecting threats that resemble past attacks, but this increasingly won’t be the case. The only way to spot unique and novel threats is to build cyber security that’s tailored to you, and that requires a whole new approach.

Smarter use of AI levels the playing field

Security teams and adversaries continue to innovate to gain the upper-hand, and the advantage of time.

Since AI equips even novice cyber criminals to mount sophisticated attacks, AI must evolve to do three things:

  • Understand and continue to learn what “normal” looks like for your unique digital environment
  • Detect and alert on any anomalous behavior the instant it occurs
  • Initiate a targeted response to contain threats and give your analysts more time, without disrupting the flow of business

Darktrace uses Self-Learning AI to understand what constitutes ‘normal’ for everyone and everything in your business, including cloud resources, identities, email accounts, endpoint devices, and even OT controllers. As the name suggests, Self-Learning AI trains itself, developing and maintaining deep understanding of ‘patterns of life’ for your business environment. Used in combination with other AI methods such as LLMs, generative AI, and supervised ML, Self-Learning AI identifies novel cyber-threats most static (backward-looking) tools miss.

The technology learns ‘on the job’ and from scratch, without relying on historical data or a massive upfront effort by your team to train the system. Probabilistic mathematics revise assumptions about behavior on a constant basis so the system keeps itself up-to-date without repeat efforts by your team.

The result is that areas of risk, as well as real-time emerging attacks, are brought to the surface – regardless of whether those attacks have been seen before in the wild.

Surgical attacks warrant surgical response

Supervised ML continues to serve a purpose, but the dawning age of novel and AI-led attacks favors a more proactive approach to securing the cloud. Tools must take greater responsibility for their own education and greater initiative via autonomous response.

What some solutions call response ultimately amounts to sending alerts and opening tickets that create more needless work for analysts. Other tools claim to automate response, but either take very limited actions like automating the process of ticket creation, or overly ambitious steps like quarantining entire systems.

Darktrace’s dynamic understanding of your environment enables a truly autonomous and precise cloud-native response. Its understanding of ‘normal’ for every user and device allows it to enforce ‘normal’ – cutting out only the malicious activity, while allowing normal business to continue functioning.

How this response will take place will depend on where Darktrace is deployed in your environment. In the network, it might mean blocking specific, anomalous connections over a certain port. In the cloud, it could mean detaching EC2 instances and applying security groups to contain only assets at risk. In email, this could be locking links or flattening attachments.

Get personal with ‘One on One’ Security

The widespread accessibility of generative AI has altered the threat landscape permanently, allowing cyber-criminals to deploy unique and personalized attacks at scale and at machine speed. In the near future, we can expect to see more novel and sophisticated phishing attacks, new automated creation of malicious code, sustained attack campaigns targeting an individual or company, and even deep fakes designed to elicit human trust.

To meet the needs of today and tomorrow, cyber security needs to leverage AI deeply and intelligently – not just using it to automate outdated historical approaches, or bolting generative AI onto existing products to keep up with the latest trend. Since 2013 Darktrace has been using AI in a fundamentally unique way: a system that learns your unique organization and understands what’s normal at a granular level. Only with this personalized understanding can you be confident in your ability as an organization to identify and shut down novel threats on the first encounter.

This form of personalized, ‘One on One’ security is a no longer a ‘nice to have’ for defenders. ‘Spray and pray’ tactics will continue to exist, but the attacks most likely to slip through the net and cause you damage are the sophisticated, the personal, and the never-before-seen. That’s what Self-Learning AI was built for – learning your business to deliver personalized cyber security, meeting every attack one-on-one.

The CISO’s Guide to Cyber AI overviews the differences between common AI approaches in cyber security and offers a high-level checklist for choosing the ideal solution for stopping attacks — including new novel threats.  To learn more about making the smartest use of AI to stop novel and targeted cloud attacks, download the guide today.

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
The Darktrace Community

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August 5, 2026

Testing a Prompt injection Attack Against an Enterprise AI Agent

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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.

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Carlo Loregian
Solutions Engineer

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August 4, 2026

Extending AI Security Visibility with Darktrace and Microsoft Agent 365

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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.

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