The scourge of “malvertising” is nothing new, but the tactic is still so effective that it's contributing to the rise of investment scams and the spread of new strains of malware.
Photo Illustration: WIRED Staff; Getty Images
Malicious digital advertisements and “SEO poisoning” that gets those ads to prime spots in search results have been mainstays of the digital scamming ecosystem for years. But as online crime evolves and malicious trends like “pig butchering” investment scams and infostealing malware proliferate, researchers say that so-called “malvertising” is still a key technique for scammers—and still a growing problem.
Instances of malvertising in the US were up 42 percent month-over-month in fall 2023 and increased another 41 percent from July to September of this year, according to data from the security firm Malwarebytes. The company says that scammers typically cycle through the advertising accounts used for malvertising quickly, and 77 percent of the accounts are only used once. The bulk of the activity, though, traces back to South Asia and Southeast Asia, Malwarebytes says, with 90 percent of the ad fraud coming from Pakistan and Vietnam, according to the researchers' telemetry. But as with many components of the digital crime ecosystem, malvertising is often offered as a service where cybercriminals from around the world can purchase ads that distribute their malware or lead potential victims to a malicious website of their choosing.
Jérôme Segura, senior director of threat intelligence at Malwarebytes, emphasizes that a particularly effective place for potential victims to encounter malicious ads is in search results, where sponsored marketing content gains legitimacy just by showing up on the same page as legitimate search results. Such malicious ads can even end up getting prime placement in the layout of search results.
“Scammers are using the power of internet and advertising technology, which allows really immense targeting of the right victim. They can get the right ad with the right intent in front of them at the right time,” Segura says. “The fact that scammers are continuing to spend money on advertising shows that these scams are working and they’re getting a return on their ad spend.”
Malvertising has been and continues to be used in phishing attacks and credit card scams, as well as for distributing malware like cryptominers and ransomware. But researchers are increasingly seeing it being used to infect victims with infostealers as well. And researchers from the United Nations Office on Drugs and Crime report that malicious ads have been incorporated into pig butchering and other investment scams, and even romance scams.
“Malvertising is a cyberattack technique that injects malicious code within digital ads,” UNODC notes in a recent report on evolving cybercrime tactics. “Difficult to detect by both internet users and publishers, these infected ads are usually distributed to consumers through legitimate advertising networks. Because ads are displayed to all website visitors, virtually every page viewer is at risk of infection.”
Researchers regularly see malicious ads in search results representing themselves as coming from legitimate businesses and organizations. Whether it's a regional municipality, a utility like a power company, or a big business, people will use search engines simply to pull up the URL of an organization. And if the first results or the most convenient results to click on are ads, scammers have the opportunity to buy this real estate.
“The volume of these things is immense,” says Sean Gallagher, the senior threat researcher at Sophos. “Search engines like Google will say they check the content of ads to ensure they’re safe, but the thing is that attackers are using ad delivery networks and can redirect the URL after the ad is paid for.”
Google is clearly aware that malicious ad activity is growing and evolving. The company specifically addresses misleading and fraudulent ad activity in its policies, including a “misrepresentation policy,” and says that it takes numerous approaches to vetting ads and detecting malvertising. Attackers have continued to develop circumvention methods, though, to avoid having their ads flagged or removed. In 2023, Google blocked or removed about 5.5 billion ads and suspended more than 12.7 million advertiser accounts.
The company has also taken steps over the years to label ads clearly and delineate them in the search results layout. Still, any search engine that’s supported by ads ultimately has the two types of content side by side, especially on mobile, where users have limited screen space.
“We expressly prohibit ads that attempt to circumvent our enforcement by disguising the advertiser’s identity to deceive users and distribute malware," Google spokesperson Nate Funkhouser told WIRED in a statement. “When we identify an ad that violates this policy, we remove it and suspend the associated advertiser account as quickly as possible.”
Sophos' Gallagher points out that criminals can often get the most for their money when buying ads for more unique searches, where they can dominate the ad space and get to the top of the results more organically. But both Sophos and Malwarebytes researchers also regularly see malicious ads running against frequent searches like those for Google, Walmart, Disney+, Slack, Lowe’s, and Apple. Segura even says that Malwarebytes itself has to invest heavily in buying search engine ads just to keep malvertising at bay for the company's brand.
“We have to defend our brand so much,” he says. “People take advantage of that.”
