As a Cyber Security leader, you make decisions every day to protect your organisation. But what if the digital ads on trusted websites were hiding a threat? Malvertising is quietly targeting organisations, slipping through defences and putting businesses at risk.
In 2023, 0.56% of digital ads in the UK were flagged as security threats—double the global average. That might sound small, but it adds up to millions of malicious adverts reaching trusted platforms. The good news? With the right knowledge and tools, you can take control and minimise the risk.
In this blog, we’ll uncover what makes malvertising such a unique challenge. We’ll explore its potential impact on organisations. And we’ll share actionable steps to help you stay ahead of this growing threat.
What Is Malvertising? Why It’s A Growing Concern For Organisations
Malvertising, short for “malicious advertising,” is exactly what it sounds like—attackers using digital ads to deliver harmful content, like malware, directly to users’ devices. Unlike traditional phishing or email-based attacks, malvertising works behind the scenes. Often, it doesn’t even need a click to cause damage.
So, how does it happen? Cyber criminals embed malicious code into legitimate ad networks. These infected ads are then distributed across countless websites, including those people trust.
You might be wondering, “Does this only affect the public? How could it harm our business?” The unfortunate truth is:
Malvertising doesn’t always play by the usual rules, and that’s what makes it tricky. Firewalls and antivirus software do a great job at blocking known threats, but they can’t catch everything. If your browser or operating system isn’t up to date, attackers can exploit those gaps to deliver malware through malicious ads.
And this isn’t just a problem for individuals. Businesses across every industry, from finance to healthcare, have been affected. The risks are real, but understanding how malvertising works is the first step in protecting your organisation.
The Risks Malvertising Can Pose To You
Malvertising can have serious consequences for organisations, affecting critical areas that are difficult to recover from:
- Reputation Damage: Even being indirectly linked to malicious activity can harm customer trust and damage your brand’s credibility.
- Data Breaches: A single malicious ad can act as a gateway for ransomware or malware, putting sensitive business and customer data at risk.
- Financial Losses: Between recovery costs, potential fines, and downtime, the financial impact can be significant.
- Operational Disruption: Malvertising can bring systems to a halt, causing downtime that disrupts business operations and productivity.
Breaking Down Malvertising
Attack Delivery Mechanisms
Malvertising is effective because it works in ways that most users—and even organisations—don’t immediately notice. Attackers embed malicious code into online ads, which are then distributed through legitimate advertising networks. These ads can deliver malware in several ways:
- Drive-by Downloads: Malware is automatically downloaded when a user visits a website displaying the malicious ad. No clicks are required, making this method especially dangerous.
- Exploit Kits: These ads scan the visitor's system for vulnerabilities—like outdated software—then exploit those gaps to deliver malware.
The clever part? Attackers often tailor their campaigns to target specific industries or demographics. For example, a financial services company might see malicious ads designed to exploit their sector-specific software or processes.
The Role of Ad Networks
Ad networks are essential for connecting advertisers with publishers, but they also create opportunities for attackers. In programmatic advertising—where ads are bought and placed automatically—there’s little time for thorough checks. This creates vulnerabilities, such as:
- Insufficient Vetting: Malicious actors exploit gaps in the review process, disguising harmful code within seemingly legitimate ads.
- Complex Supply Chains: Ad networks often rely on third parties to deliver ads, which can obscure the source of malicious content and make it harder to identify threats.
- Cloaking Techniques: Attackers use methods to hide malicious behaviour during ad reviews, only activating the harmful code once the ad is live.
The result? Even trusted websites can unknowingly host malicious ads. For organisations, this means traditional Cyber Security defences aren’t enough. A layered approach to security is essential to protect your systems and users from these hidden threats
Preventing Malvertising in Your Organisation
Stopping malvertising isn’t just about recognising the threat—it’s about taking proactive steps to reduce exposure and protect your organisation. Here’s how Cyber Security leaders can keep their teams safe from malicious ads:
1. Educate Employees on Malvertising Risks
Awareness is your first line of defence. Train your teams to:
- Avoid clicking on ads, even on trusted websites.
- Spot suspicious behaviour, such as unexpected redirects or pop-ups.
- Report anything unusual to IT immediately.
A short, targeted Cyber Awareness session can go a long way in reducing human error.
2. Use Ad Blockers Across the Organisation
Deploy ad blockers on all devices used for work. These tools prevent ads from being displayed, cutting off malvertising threats at the source.
3. Secure Browsers and Endpoints
Make sure every device is configured securely by:
- Keeping browsers up to date to patch vulnerabilities.
- Using endpoint protection software to detect and block malicious activity.
- Configuring firewalls to block access to known malicious domains.
Here’s an extra layer of reassurance: if your antivirus and browser are fully updated, they’re likely to block malicious code before it can cause any harm—even if someone clicks on a compromised ad. Auto-downloads or silent infections typically only happen when there’s an unpatched vulnerability.
4. Monitor Network Activity for Unusual Behaviour
Regular monitoring helps detect threats early. Look out for:
- Unusual traffic patterns or spikes.
- Devices connecting to suspicious or unauthorised domains.
- Unexpected software downloads or installations.
Tools like Secure Web Gateways or DNS filtering can add extra layers of protection.
5. Limit Admin Privileges and Enforce Policies
Reduce the potential impact of malvertising by:
- Restricting admin privileges to only those who truly need them.
- Implementing strict browsing policies, such as limiting access to non-work-related sites.
- Ensuring downloads are restricted to trusted sources.
The NCSC’s Role and Recommendations
The National Cyber Security Centre (NCSC) guidance focuses on creating a safer digital advertising ecosystem by reducing opportunities for malicious activity.
While much of their advice targets advertising partners, there are actionable steps organisations can take to align with these recommendations and strengthen their own defences:
- "Know Your Customer" Checks
The NCSC emphasises the importance of verifying the identity of anyone involved in digital advertising transactions. While this principle applies to ad partners, organisations can adapt it internally by vetting the websites and platforms their employees access. Restrict access to unverified or non-business-related sites to reduce exposure.
- Use Data from Reputable Sources
Just as ad networks should rely on trusted data, organisations can ensure that their teams only interact with verified websites. Use tools like DNS filtering to block access to potentially harmful domains and ensure that your browsing policies are enforced across the board.
- Adopt Industry Standards for Security
While organisations may not directly manage advertising processes, you can still benefit from understanding how security standards like ads.txt and buyers.json help prevent malicious ads. These standards promote transparency and can inform the tools you use to evaluate and monitor your network traffic.
Real Life Examples To Keep You In The Loop
1. Finance Department Targeted via Search Engine Ads
In 2023, a Managed Defence team identified a malvertising campaign where attackers used sponsored search engine results to distribute backdoor malware. Cyber criminals purchased ads that appeared when users searched for financial software tools. Employees in finance departments, seeking legitimate software, clicked on these ads and were redirected to malicious sites that installed malware, compromising sensitive financial data.
- Lesson Learned: Ensure that employees access software directly from official vendor websites rather than through search engine ads. Implementing ad blockers and educating staff about the risks of malvertising can mitigate such threats.
2. Human Resources (HR) Department Exploited through Job Advertisement Platforms
Attackers have exploited online job advertisement platforms by embedding malicious code into ads for job postings. HR personnel, while reviewing applications, encountered these compromised ads, leading to the download of malware onto their systems. This breach provided attackers with access to personal data of applicants and internal HR records.
- The Takeaway: HR departments should use reputable job platforms with robust security measures. Regular training on recognising suspicious ads and maintaining updated security software is essential to prevent incidents.
Staying Ahead Of Malvertising One Step At A Time
Malvertising is a stealthy yet significant threat that organisations cannot afford to ignore. By understanding how it works and implementing proactive measures—like employee training, robust security tools, and regular monitoring—you can stay ahead. Collaboration and vigilance are key to protecting your organisation from potential breaches and reputational damage.
At Equilibrium Security, we’re here to support you in strengthening your Cyber Security against threats like malvertising. If you’re ready to safeguard your organisation, get in touch with us today on 0121 663 0055 or email us at enquiries@equilibrium-security.co.uk.
Ready to achieve your security goals? We’re at your service.
expertise to help you shape and deliver your security strategy.
About the author
