Most marketing agencies don't think of themselves as high-value targets for a cyber attack. Banks get attacked. Hospitals get attacked. A brand agency in Shoreditch… probably not worth the effort, surely?

That assumption is increasingly difficult to sustain. According to the UK Government's Cyber Security Breaches Survey 2024, 50% of UK businesses experienced a cyber breach or attack in the last 12 months. The methods have also narrowed: phishing alone accounted for 84% of those incidents, with no sophisticated hacking required, just a convincing email and an unlucky click.

For marketing agencies, the exposure is real and specific. That’s why this article sets out what data agencies are actually responsible for, where the most common vulnerabilities tend to sit, and what the legal obligations look like if something goes wrong.

We’ll discuss: 

• What data do marketing agencies actually hold, and why does it matter?
• What are the most common cyber attacks on marketing agencies?
• What are your GDPR obligations as a marketing agency?
• How should a marketing agency protect client data and creative assets?
• What should you do if your agency suffers a data breach?

Let’s start from the beginning.

What data do marketing agencies actually hold, and why does it matter?

It's worth being concrete about this, because the answer tends to be broader than agencies initially assume.

At any given time, a marketing agency is likely holding some combination of the following on behalf of clients: unreleased campaign creative, brand strategy documents, consumer research and audience data, media plans, contractual terms, and, particularly for agencies running paid media or CRM programmes, personally identifiable information (PII) about end consumers.

Beyond client data, there's the agency's own operational data: employee records, financial information, supplier contracts, new business proposals, and proprietary methodologies that represent genuine intellectual property.

Under the UK GDPR and the Data Protection Act 2018, agencies that process personal data on behalf of clients are classified as data processors. Where agencies collect or use personal data for their own purposes, running their own marketing, maintaining a client contact database, they become data controllers. Both roles carry legal obligations, and the distinction matters when it comes to understanding what you're accountable for.

The practical upshot: if your agency handles personal data in any form (and almost every agency does) you have data protection responsibilities that go beyond keeping a folder locked.

What are the most common cyber attacks on marketing agencies?

Understanding where threats typically come from is more useful than a general awareness that threats exist.

Phishing

Phishing is by far the most prevalent. The DCMS 2024 survey found it accounts for 84% of cyber incidents across UK businesses. For agencies, the risk is compounded by the volume of external communication involved in the work: new client introductions, freelancer onboarding, supplier invoices, press releases, vendor pitches. A well-crafted phishing email fits naturally into that flow, and most people won't scrutinise every link they receive during a busy week.

Ransomware

Ransomware has grown significantly as a threat to SMEs. Attackers encrypt a company's files and demand payment for restoration. For an agency mid-campaign, losing access to a shared asset library or project management platform, even temporarily, can have serious consequences for client delivery and reputation. The UK's National Cyber Security Centre (NCSC) has noted that ransomware remains one of the most significant cyber threats facing UK organisations.

Business email compromise

Business email compromise (BEC) is less talked about but financially damaging. It typically involves an attacker impersonating a senior member of staff or a trusted supplier to redirect payments or extract sensitive information. Agencies, which handle supplier relationships, freelancer payments, and client invoicing regularly, are a natural target.

Weak access management

Weak access management is less of a threat in itself and more of a condition that makes other threats more damaging. Former employees retaining system access, shared login credentials, or admin rights granted too broadly are among the most common findings when agencies review their security posture. They're also among the easiest to address.

What are your GDPR obligations as a marketing agency?

This is the area where many agencies find themselves underprepared; not through negligence, but because the obligations aren't always clearly communicated.

Under UK GDPR, the key requirements for agencies handling personal data include:

• Lawful basis for processing: Every use of personal data needs a documented lawful basis. For agencies running paid media with audience targeting, or managing client CRM data, understanding which basis applies, and being able to demonstrate it, is a baseline requirement.
  
  
• Data processing agreements (DPAs): Where an agency processes personal data on behalf of a client, a DPA should be in place between the two parties. This is a legal requirement under UK GDPR Article 28, not a commercial nicety. Many agencies operate without them, which creates liability on both sides.
  
  
• Breach notification: If a personal data breach occurs, whether through a cyber attack, accidental disclosure, or lost device, organisations are legally required to notify the ICO within 72 hours of becoming aware of it, provided the breach is likely to result in a risk to individuals' rights and freedoms. Where the risk is high, affected individuals must also be notified. The ICO's guidance on breach reporting is worth familiarising yourself with before you need it.
  
  
• Data retention and deletion: Personal data should not be held for longer than necessary. In practice, this means having a policy that defines retention periods for different data types, and actually following it. Campaign data sitting in shared drives years after a client relationship has ended is a common and easily avoidable compliance gap.
  
  
• Staff awareness: The DCMS 2024 survey found that only 33% of UK businesses have a formal cybersecurity policy. For agencies, where staff regularly interact with external parties and handle sensitive materials, training people to recognise phishing attempts and handle data appropriately is a practical and proportionate step.

How should a marketing agency protect client data and creative assets?

There's no single measure that resolves cyber risk, but there are a set of practices that, applied consistently, significantly reduce an agency's exposure.

• Access controls and user management: Not everyone in an agency needs access to everything. Applying the principle of least privilege, where people have access only to what they need for their specific role, limits the damage that any single compromised account can do. This also means promptly removing access when someone leaves, which sounds obvious but is frequently overlooked in busy agency environments.
  
  
• Multi-factor authentication (MFA): Enabling MFA across email, cloud platforms, and any system accessible from outside the office is one of the highest-impact, lowest-cost security measures available. It significantly reduces the effectiveness of phishing attacks, since a stolen password alone is no longer sufficient to gain access.
  
  
• Endpoint management: Laptops and mobile devices used for work, especially in hybrid setups, should be enrolled in a device management system that enforces security policies, allows remote wipe if a device is lost or stolen, and ensures software is kept up to date. A device running unpatched software is a straightforward entry point for attackers.
  
  
• Secure file sharing and collaboration: Consumer-grade file sharing tools aren't designed with business security in mind. Using properly configured cloud environments, with appropriate permissions, audit trails, and encryption, for sharing client materials protects both the agency and the client.
  
  
• Regular backups: In the event of a ransomware attack or accidental data loss, recent backups are often the difference between a recoverable incident and a catastrophic one. Backups should be automated, tested periodically, and stored in a way that keeps them separate from the primary environment.
  
  
• Cyber insurance: According to the DCMS 2024 survey, only 43% of UK businesses have cyber insurance. For agencies holding client data and creative IP, it's worth understanding what a policy covers, and what it doesn't, before an incident occurs rather than after.

What should you do if your agency suffers a data breach?

The first 72 hours matter more than most agencies realise. Having a clear plan before anything goes wrong is considerably better than improvising under pressure.

• Contain the incident: Isolate affected systems where possible to prevent the breach from spreading. If a device has been compromised, disconnect it from the network.
  
  
• Assess the scope: Understand what data has been affected, how many individuals it relates to, and whether there is ongoing risk. This assessment informs every subsequent decision.
  
  
• Notify the ICO if required: Where a breach is likely to result in a risk to individuals, the ICO must be notified within 72 hours. The online reporting form takes approximately 30 minutes to complete: having the relevant information ready in advance makes this significantly less stressful. The ICO is clear that reporting early, even with incomplete information, is preferable to waiting until the full picture is known.
  
  
• Notify affected individuals if the risk is high: Where a breach poses a high risk to the rights and freedoms of individuals, such as financial data, health information, or sensitive personal details, those individuals must also be informed without undue delay.
  
  
• Document everything: Whether or not the breach meets the reporting threshold, all personal data breaches must be documented internally. This is a UK GDPR requirement and provides important protection if the breach is later scrutinised.
  
  
• Review and learn. What happened, why it happened, and what would prevent a recurrence. The ICO's guidance encourages organisations to treat every incident as an opportunity to strengthen their approach.

Only 34% of businesses that identified a breach in the DCMS 2024 survey reported it to any external party. That number is low… and in cases where reporting is legally required, it represents a significant compliance risk.

Cybersecurity for marketing agencies isn't a separate discipline from running a good agency. It's part of it. The agencies that handle client data responsibly, maintain secure systems, and have a clear plan for when things go wrong are in a stronger position, commercially and legally, than those that treat security as someone else's problem.

If you'd like to understand where your agency's current setup stands, Lyon Tech works with marketing and advertising agencies across London on exactly this. Get in touch with the team to start the conversation.