Medical IT Support

What is Malvertising and How to Protect Yourself from it?

Malvertising: Risks
and Protection

Online advertising keeps much of the internet free. It funds newsrooms, blogs, apps, and services you use every day. But the same ad ecosystem that makes digital content accessible can also be abused by cybercriminals. One of the most common tactics is malvertising-short for malicious advertising-where malware is distributed through online ads.

Our cybersecurity team at Computing Australia Group (Perth) has been engaged frequently over recent months to remediate incidents triggered by malicious ads. What makes malvertising especially frustrating is that it can affect c areful users and reputable websites. In some cases, you don’t even need to click. A compromised ad placement, a rogue ad network, or a malicious redirect can be enough.

This guide explains what malvertising is, how it spreads, how to spot the warning signs, and what you can do-today-to reduce your risk on phones, tablets, and computers.

What is malvertising?

Malvertising is the use of online advertisements to deliver malware, redirect users to harmful websites, or trick people into installing malicious software. A “malicious ad” can appear in places you’d normally trust: large news sites, popular blogs, streaming services, or mobile apps. That’s because ads often come from third-party ad networks and are delivered through complex, automated bidding systems. Attackers exploit that complexity to sneak harmful content into the ad supply chain. Malvertising can result in:

Drive-by downloads (malware installs without clear user action)
Credential theft (fake login pages, session hijacking)
Scams and fraud (tech support pop-ups, “your phone is infected” alerts)
Ransomware infection (in more severe cases)
Browser hijacking (unwanted extensions, homepage/search changes)
Data exposure (spyware, keyloggers, tracking)

How malvertising works

Malvertising isn’t one single technique—it’s a delivery method. The “payload” can vary from nuisance adware to serious malware. Here’s a simplified view of how it typically happens:

1) Attackers create or compromise an ad

They may:

2) The ad is served through the ad ecosystem

Because ad delivery is automated and distributed, malicious ads can be served at scale before detection kicks in—sometimes in minutes, sometimes over days.

3) The user is redirected or tricked

Depending on the attack:

Clicking the ad sends the user to a malicious landing page
The ad triggers a redirect without an obvious click (in some scenarios)
A pop-up imitates a system warning, urging urgent action
The user is guided to install a “security tool,” “update,” or “extension”

4) The payload executes

The end result might be:

A downloaded file (often disguised as a document, update, invoice, etc.)
A browser extension install
A fake login prompt (credential harvesting)
Malware execution via a browser or plugin vulnerability (less common today than in the past, but still possible, especially on outdated systems)

Why malvertising is hard to detect

Malvertising is effective because it blends into normal browsing and often avoids obvious red flags. A few reasons it slips through:

Ads are dynamic: The same ad slot may display different content to different users.
Attackers “cloak” content: They show harmless content to moderators or scanners, then deliver malicious content to real users.
The supply chain is layered: Websites may rely on multiple ad partners, resellers, and exchanges—making accountability difficult.
Time-based attacks: Some malicious ads stay dormant until certain conditions are met (time, geography, device type, browser).
Social engineering works: Even when the technical path is blocked, scare tactics (“Your device is infected!”) can push users into installing something dangerous.

Common malvertising tactics and formats

Here are the patterns we see most frequently:

Fake system alerts and tech support scams

You’ll see pop-ups claiming:

These are designed to panic you into:

“Update required” prompts

Malvertising often imitates:

Legitimate browsers update through their own built-in mechanisms—not random pop-ups.

Malicious redirects

A click—or even a page load—can bounce you through multiple URLs and land you on:

Drive-by download attempts

Modern browsers are more resistant than they used to be, but outdated software, insecure extensions, or misconfigured systems can still be vulnerable.

Malicious or shady browser extensions

Some ads push extensions that:

Malvertising vs adware vs phishing: what’s the difference?

These terms overlap, but they are not identical:

Malvertising

Malvertising is the use of ads to deliver malware or scams. It’s about the delivery channel: advertising.

Adware

Adware is software that displays ads—often bundled with free applications. Some adware is merely annoying; some becomes dangerous when it:

Phishing

Phishing is the attempt to trick you into handing over sensitive information (passwords, codes, payment details). Phishing can be delivered via:

In short: malvertising uses ads as the vehicle; adware is typically software that pushes ads; phishing is a deception technique that may appear inside ads.

How to identify malvertising ads

Not all online ads are harmful—but certain patterns should put you on alert. Be cautious if you see ads that include:

Spelling or grammar errors (especially brand names spelled incorrectly)
Celebrity scandals or sensational clickbait (“shocking secret…”, “you won’t believe…”)
Miracle cures or unrealistic health claims
Over-the-top urgency (“Act in 5 minutes”, “Account will be locked”)
“Get rich fast” promises
Low-quality designs or mismatched branding
Adult/pornographic content in contexts where it doesn’t belong
Fake download buttons (especially on file-sharing or streaming sites)
Unexpected redirects when you click anywhere on a page
Pop-ups that mimic your device (fake Apple/Google/Microsoft warnings)

A practical rule: if an ad tries to make you feel panic, greed, or urgency, treat it as suspicious until proven otherwise.

How to protect yourself from malvertising

The best protection is layered: safer browsing habits + browser hardening + endpoint security + keeping systems updated.

1) Don’t click ads you don’t fully trust

This is the simplest and most effective baseline. If an offer looks interesting, don’t click the ad—go to the brand directly.

Safer alternative: open a new tab and type the company name (or use a bookmark you trust).

2) Use “click-to-play” (or reduce auto-play)

Auto-playing media isn’t just annoying—it can increase risk and distractions.

Browsers vary, but most provide controls under:

3) Install a reputable ad blocker (or use a browser with tracking protection)

Ad blockers can reduce exposure to malicious ad inventory—especially on high-risk sites.

Options include:

Tip: Keep your extensions minimal. Too many extensions increases attack surface.

4) Keep your browser, OS, and apps updated

Outdated software is one of the most common risk factors. Updates patch known vulnerabilities that malvertising chains sometimes rely on.

5) Use reputable endpoint protection (antivirus/anti-malware)

Modern endpoint protection can block:

Make sure:

6) Download only from official sources

For apps, plugins, and extensions:

Avoid “download portals” and random mirror sites, especially for popular software.

7) Lock down browser permissions

A lot of malvertising damage comes from permission abuse.

Review and restrict:

If you see a site repeatedly asking for permission—leave.

8) Use a password manager + MFA

If malvertising leads you to a fake login page, a password manager often won’t autofill—this is a subtle but powerful warning sign.

Also enable multi-factor authentication (MFA), ideally using an authenticator app or security key for high-value accounts (email, banking, admin accounts).

9) Consider network-level protection

For households and businesses, network-level controls can reduce risk:

Avoid “download portals” and random mirror sites, especially for popular software.

Protection tips for businesses and website owners

If you run a website that displays ads, malvertising is also a brand and trust risk—even if you’re not the attacker. Consider:

Vet ad partners and reduce reseller complexity

Work with reputable ad networks and avoid excessive layers of resellers. Complexity increases blind spots.

Use security headers and strong site hygiene

Monitor and respond quickly

Separate ad-related scripts where possible

Limit script privileges and isolate third-party scripts to reduce blast radius.

What to do if you think you’ve been hit

If you clicked an ad and something feels off, act quickly but calmly.

Step 1: Close the tab (don’t interact with pop-ups)

If a page says “Call now” or “Your device is infected,” don’t click anything inside it. Close the browser tab or the browser itself.

If it won’t close:

Step 2: Check for suspicious downloads

Look for recently downloaded files you didn’t intend to download. Don’t open them.

Step 3: Run a full security scan

Use reputable endpoint protection and run a full scan. If threats are detected, follow the remediation steps.

Step 4: Remove suspicious extensions

In your browser extension settings:

Step 5: Change passwords if you entered credentials

If you typed a password into a site you now suspect was fake:

Step 6: Watch for persistence

Signs the problem isn’t gone:

If symptoms persist, professional assistance can save time and reduce damage – especially for business devices.

Ads may be striking, but they can be harmful. Following safe online practices can protect you from malvertising. To know more, contact our cybersecurity specialists or email us at cybersecurity@computingaustralia.group.

Jargon Buster

Browser – is an application for accessing data on the Internet.

Malware – a term for Malicious Software that is intended to cause harm to devices, networks and servers. Common types include viruses, ransomware, spyware etc.

Pop-ups – pop-up ads are forms of online advertisement that are graphical user interface display areas that suddenly appear in the visual interface.

Malvertising: Risksand Protection