malvertising and malware ads

Introduction

Most people think of online ads as annoying, but not dangerous. A banner pops up. A video auto-plays. A sponsored link slides into your search results. Most of the time, you scroll past it and move on.

At the same time, we’ve become very familiar with personalized ads that use our prior search history to determine what might pique our interests. These ads are not just background noise anymore. They are a massive potential entry point for online threat actors.

Malvertising (the portmanteau of malicious advertising) is a tactic where attackers use online ads to deliver malware, steal information, or redirect users to harmful sites. These ads often appear on legitimate, well-known websites, which makes them hard to spot and easy to trust.

How Does Malvertising Work?

Malvertising does not usually rely on shady websites or obvious scams. Instead, attackers purchase ad space through real advertising networks, just like legitimate marketers do.

Once the ad is approved and running, it may:

  • Redirect users to a malicious website: In fact, 68% of mobile malvertising involves redirecting users to new websites.
  • Exploit browser or plugin vulnerabilities: By infecting your browser, threat actors can then track your activity online and steal private information that you enter.
  • Download dangerous software: Once installed on your device, they can encrypt your files in a ransomware attack or unleash keyloggers that spy on your private communications and snag login credentials.
  • Lead to a fake update or login page: Clicking on an infected button online, or entering your sensitive PII into compromised landing pages, can further compromise your device and data security.

In some cases, simply loading the page is enough to trigger malware. You do not have to click the ad for it to cause harm; it automatically loads without your knowledge or consent.

Why Malvertising Is So Effective

Malvertising works because it blends into normal online behavior. Because ads are often served dynamically and change constantly, security teams may not even see the same ad that infected a user.

Users trust familiar websites. They expect ads to be annoying, not hostile. They are also conditioned to click sponsored results that look professional and relevant.

Attackers take advantage of this trust in several ways, including:

  • Mimicking well-known brands
  • Copying legitimate software update prompts
  • Using clean-looking graphics and language
  • Rotating malicious code to avoid detection

By the time the host site flags and removes the ad, it may have already reached thousands of users.

Risk to Work Devices and Data

Malvertising becomes especially dangerous when it reaches work devices.

A single infected endpoint can:

  • Capture login credentials
  • Install spyware or keyloggers
  • Open a backdoor into corporate systems
  • Enable lateral movement across a network

Remote and hybrid work environments significantly amplify this risk. Some people browse the web for legitimate work reasons, and on devices that have access to sensitive systems. That makes clicking one infected ad all the more costly.

Why Ad Blockers Alone Are Not Enough

Ad blockers can reduce exposure, but they are not a complete solution on their own.

Why? Some malicious ads bypass your malware blockers entirely. Other malvertisements deliver their payload through formats that many blockers allow by default. Some managed environments may not even permit the use of ad blockers. Therefore, relying solely on blocking tools creates a false sense of security.

In other words: Your awareness and behavior still matter.

How to Reduce Malvertising Risk

To best avoid falling victim to this scam, you should focus on reducing their opportunity and impact. Some good habits to adopt include:

  • Keep browsers, plugins, and operating systems fully updated
  • Avoid “update” prompts that appear inside ads or pop-ups
  • Only download software from official vendor websites
  • Be cautious with sponsored search results
  • Report suspicious ads to IT or your security team

If an ad feels urgent, alarming, or out of place, that should raise your alarm bells.

Conclusion

Malvertising is effective because it hides in plain sight. It does not look like an attack. Instead, it looks like the internet doing what it always does, which includes providing you with targeted promotions.

As attackers continue to exploit trusted platforms and everyday behaviors, cybersecurity depends less on spotting obvious red flags and more on understanding these subtle risks. Online ads are no longer just a marketing channel. In the wrong hands, they can deliver malware directly to your computer…without you even noticing.

Taking into account these cyber-risks, and adjusting how you browse and online shop accordingly, can be the difference between a harmless click and a costly data breach!

The post Malvertising: When Online Ads Become a Delivery System for Malware appeared first on Cybersafe.