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Learn What Adware Is Before It Destroys Your Computer

 By Charles Joseph | Cybersecurity Researcher
 Published on November 25th, 2022
This post was updated on November 25th, 2023

Let’s be honest: even when ads are subtle, compact, unassuming, and inoffensive, most of us don’t really like them.

They interrupt your browsing flow and hijack your attention, making you feel pressured to spend money or time on whatever the ad is trying to sell you. Luckily, we’re usually pretty good at ignoring them or blocking them out — and sometimes, they can even end up being interesting or useful to us.

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But when you’re infected with adware, all of that changes for the worse.

What Is Adware?

In broad terms, adware refers to any ad-supported software — that is, software that earns its creator revenue by displaying ads to the user.

But the term is usually used to describe ad-supported software that installs itself on your computer without warning, assaults you with ads even when the program isn’t running, or even loads so many ads that your computer crashes.

Though this malicious adware isn’t usually as harmful as a Trojan or ransomware, it’s still not something you want anywhere near your device.

How Adware Spreads

Adware spreads through pop-up ads

Malicious adware usually spreads via one of two vectors: as a potentially unwanted program that gets downloaded alongside other software or as a drive-by download.

Potentially Unwanted Programs

When you download software, you’re usually asked to agree to the software’s end user license agreement (EULA) during the installation process.

You may also be asked to select which components of the software to install, with the recommended choice being to install the full version of every component.

Most people breeze through this process, simply agreeing to whatever the installer suggests. Malicious adware creators know this, and they take full advantage of it by hiding their adware within these steps.

One of the dense, wordy clauses in the EULA, for example, may be that all users must agree to be shown pop-up ads whenever the program is running. Or one of the “components” of the software may be a totally separate program whose sole purpose is to run constantly in the background and display ads.

And in some cases, the software you’re intentionally installing may not warn you at all about the presence of additional adware.

In any event, this type of adware is known as a potentially unwanted program or PUP. It’s a program that gets installed discreetly alongside other software without the user being made fully aware of its presence or purpose.

Drive-By Downloads

A malicious file is downloaded

New browser and network vulnerabilities are discovered every day, some of which are used by bad actors to load your computer up with adware without your knowledge.

A website you visit may be compromised with malicious code, automatically downloading and installing adware as soon as you load the page. Or a hacker may configure a public WiFi network to redirect all users to the adware download.

These so-called drive-by downloads happen so quickly and so subtly that many victims don’t notice that anything has been downloaded to their computer.

What Adware Does

Once it’s on your computer, adware gets to work, causing any or all of the following symptoms.

Displays Excessive, Inappropriate Ads

If you’re infected with adware, you may notice multiple pop-up ads appearing as soon as you connect your computer to the internet, then continuing to appear throughout the day, no matter what you’re doing.

These ads may move around or sport fake exit buttons, making it difficult or impossible to close them. They may continually jump to the front of your screen, preventing you from using your other programs.

What’s more, these ads are often vulgar, pornographic, or scammy, promoting adult websites, get-rich-quick schemes, fake antivirus programs, or other inappropriate content.

Alters Browser and Internet Settings

Adware may add toolbars, extensions, or notifications to your browser without your consent, giving it even more space in which to display ads.

It may change your homepage to one that’s laden with ads or automatically open ads in new tabs. Some adware even alters your default search engine or causes every site you visit to redirect to a different, often unsafe, one.

Even sites you visit regularly may be affected by adware, as it can modify your browser to prevent other providers’ ads from loading. Sites that rely heavily on ads and trackers, like Facebook and Google, may not function or display correctly.

Consumes System Resources

Loading so many ads can place a huge demand on network and system resources, especially on older devices.

Adware victims may find that all of their RAM and processing power is being eaten up by ads, while others on the network might find that there’s not enough bandwidth left to do anything online.

In severe cases, adware can cause your browser to crash repeatedly. And if you run out of RAM, your entire OS may crash, forcing you to restart your computer and potentially lose data.

Harvests User Data

Some adware contains a spyware component. Spyware is malicious software that monitors your browsing history, search history, usage habits, and even keystrokes.

This data is typically used to make the adware more effective, enabling it to serve you more targeted ads that you’re more likely to click on.

But this data can also be sold to data brokers — companies that buy and sell personal data in bulk. Worst of all, this data is also used by hackers to steal your passwords, credit card numbers, and other private, sensitive information.

Earns the Adware Creator and Distributor Money

There’s one thing that all adware has in common: it earns the creator and/or distributor money.

Developers of free software are often approached by adware creators, who offer them money in exchange for bundling the adware with each software download. The adware creators themselves may earn money each time an ad is clicked or earn a smaller amount each time an ad is viewed.

Key Adware Takeaways

Spreads adware
  • Adware can refer to any piece of software that contains ads, but it’s most often used to refer to unwanted software with excessive, obtrusive, or malicious ads.
  • Adware is often installed unknowingly alongside legitimate software, though it can also infect your computer via compromised websites.
  • Some adware can overwhelm your computer with ads, causing it to slow down or crash.
  • Adware may alter your browser’s settings, interfere with the functions of various websites or redirect your web traffic to unsafe sites.
  • Adware generates revenue each time an ad is viewed or clicked, prompting creators to make their adware as aggressive as possible.

History of Adware

In the early 1990s, adware had a more innocent connotation than it does today. Back then, it referred to any ad-supported program, most commonly free software that featured a small text-based ad for one of the creator’s other programs.

But as the ad industry went digital in the late ’90s and early ’00s, adware’s reputation worsened rapidly. Large companies began offering small developers hefty sums in exchange for packaging adware with their programs, and many developers took them up on it.

From there, adware and consumers were caught in a cat-and-mouse game. As users wised up to adware and ad-related scams, adware creators had to get craftier, incorporating tracking into their adware to create targeted ads.

By the late 2000s, consumers were absolutely flooded with adware, and authorities began issuing large fines to adware creators in an attempt to end the scourge.

Those efforts took down a few individual players, but adware as a whole simply got more sophisticated, using encryption and advanced tactics like rootkits to evade detection and removal. Today, it’s still one of the top cybersecurity threats, especially on mobile devices.

Adware by the Numbers

Famous Adware

The Fireball Adware

Infecting over 250 million computers and a whopping 20% of corporate networks worldwide, Fireball is one of the most prolific pieces of adware ever created.

First spotted in 2017, Fireball modifies victims’ homepages and search engines, preventing them from changing their browser settings while tracking all of their browsing history. This data is then used by the creator, a Chinese marketing company, to serve targeted ads.

But Fireball is coded in such a way that it can easily run other unauthorized code, steal login credentials and download other malware, making it far more dangerous than meets the eye.

The Gator Adware

One of the earliest examples of malicious adware, the Gator eWallet was a big deal when it debuted in 1998. A free program, it purported to be a powerful digital wallet, storing users’ passwords, credit card numbers, and form data for auto-filling.

But it secretly inserted itself into downloads of other software, spied on users’ browsing data, and replaced ads on other websites with its own. These processes causes many users’ computers to slow to a crawl, and the software itself was very difficult to uninstall.

After several class-action lawsuits and a decade of bad publicity, Gator’s parent company, Claria, shut down in 2008.

What Is Adware? (Video)

"Amateurs hack systems, professionals hack people."
-- Bruce Schneier, a renown computer security professional
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