What Is Malvertising? How Ad-Based Malware Is Hitting Businesses
Neil Hare-Brown- 2 days ago
- 3 min read
You Google a popular tool — “download Slack”, “get AnyDesk”. The first result looks official. You click the ad — and malware silently downloads in the background.
Malvertising — short for malicious advertising — is becoming one of the most effective ways for attackers to deliver malware to business users.
These aren’t sketchy pop-ups from 2005 — they’re well-crafted, high-ranking search ads or legitimate-looking banners on real sites.
They don’t need phishing emails or compromised credentials — just one click on a convincing ad.
In this blog, we’ll explain how malvertising campaigns work, what makes them so dangerous, and how your organisation can defend against them.
What Is Malvertising?
Malvertising is the use of online advertising to deliver malware to unsuspecting users. It often appears as:
Search engine ads:
Fake Google or Bing ads impersonating trusted brands (e.g. “Zoom”, “WinRAR”, “TeamViewer”)
Display ads:
Banners or sidebars on legitimate websites served through third-party ad networks
Redirect chains:
Clicking the ad silently sends the user through multiple URLs, landing them on a malicious site
Once clicked, users may be prompted to download malware disguised as legitimate software — or they may be infected automatically via a drive-by download.
Real-World Examples of Malvertising Attacks
AnyDesk & WinSCP Malverts
Attackers ran paid Google Ads for remote access tools. Victims clicking the ad were taken to fake download pages delivering malware loaders such as IcedID or RedLine Stealer.
Malicious PDF Campaigns
SEO-poisoned ads led to fake documentation pages. Victims downloaded PDFs that appeared normal but launched scripts to install malware.
FakeUpdate / SocGholish Tie-In
Malvertising has been used to funnel users into the FakeUpdate framework, tricking them into installing browser updates that delivered remote access trojans.
Why Malvertising Is So Effective
✅ It mimics trusted behaviour:
Users expect to click ads for software or services.
✅ It uses legitimate infrastructure:
Ads are served by platforms people rely on.
✅ It bypasses email defences:
No phishing email means no trigger for email security tools.
✅ It can be hyper-targeted:
Ads can be placed by geography, industry, or keyword — increasing success rates.
These attacks often bypass standard perimeter controls, particularly if browser access and user permissions aren’t tightly managed.
How to Protect Your Business from Malvertising
Block Ads Where Possible
Use browser-based ad blockers or network-level tools to reduce exposure to potentially malicious ads.
Restrict Software Downloads
Prevent users from downloading and installing software without approval. Use centralised update management wherever possible.
Implement DNS Filtering
Web filtering tools can block known malicious domains, even if users click on a bad link.
Deploy Endpoint Detection & Response (EDR)
Modern malware often evades legacy antivirus. EDR solutions can catch suspicious behaviours — not just known signatures.
Train Staff to Recognise Risks
Make sure employees know that the top search result isn’t always safe — especially if it’s labelled “Ad”.
Monitor Browsing Behaviour
Look for anomalies, such as visits to known bad domains or unusual download activity.
What to Do If Someone Has Clicked a Suspicious Ad
✅ Isolate the device
Disconnect from the network to prevent spread.
✅ Check for malware
Run a full endpoint scan to detect payloads like stealers or loaders.
✅ Investigate lateral movement
Look for privilege escalation or unauthorised access.
✅ Review browsing history
Identify whether others may have been exposed.
✅ Engage incident response
Storm Guidance can help assess and contain the threat.
How STORM Guidance Can Help
✔ Malvertising-related incident response
We investigate and contain malware infections stemming from fake ads, SEO poisoning, or drive-by downloads.
✔ Endpoint and browser security reviews
We assess your systems for vulnerabilities in ad exposure, download permissions, and browser configuration.
✔ Cyber awareness training
We help educate your staff on emerging threats like malvertising, fake updates, and malicious search results.
✔ Threat actor engagement
If malware has led to data theft or extortion attempts, our experts can engage threat actors and manage ransom demands.
✔ Strategic cyber resilience support
From incident readiness to policy development, we help strengthen your cyber defences against ad-based and social engineering threats.
Final Thoughts
Malvertising doesn’t rely on tricking your email system — it targets your users' trust in search engines and websites.
With a single click, attackers can bypass your perimeter and plant malware inside your business.
By limiting exposure to ads, managing downloads centrally, and investing in modern endpoint protection, you can stay ahead of these evolving threats.
To prepare for advanced tactics like malvertising and drive-by downloads, explore Storm Guidance’s ransomware support and cyber incident response services.
