Advertising may sometimes seem like an expensive business, but injecting malware into online ads, or malvertising, is turning out to be a cheap way for cybercriminals to reach their victims, according to a recent research report.

Security firm Malwarebytes said malvertising is running much like legitimate ad campaigns, where cybercriminals pay a certain amount for playing malicious software on a popular website. The firm’s report indicates that, for as little as 80 cents, 1,000 consumers can be hit at once, with zero-day attacks aimed particularly at Flash Players that help serve up multimedia content online.

Unfortunately, as Infosecurity Magazine pointed out, the ongoing movement to make legitimate online advertising more targeted to specific individuals may make malvertising even more effective in the future. For example, malware victims may be identified by age, gender, the location from which they’re surfing the Internet and so on. Marketers expect these filters to make sure they’re getting the most bang for their advertising buck, and cybercriminals can benefit just as much from the real-time bidding engines that power such campaigns.

Although the Malwarebytes report suggested high-profile sites such as The Huffington Post were among those infected by malvertising, SC Magazine recently reported on a rogue advertiser that spread malware across nearly a dozen adult websites, some of which draw tens of millions of regular monthly visitors. What’s interesting is that the online ads in question are pulling double duty in many of these cases, serving the exploit and the malware at the same time rather than redirecting visitors to a third-party site.

While the rest of the world is still getting up to speed on the extent of these threats, some major organizations are already taking matters into their own hands. Facebook, for instance, was among those hit with a video ad that infected 110,000 users in two days, according to The Inquirer. As a result, ITProPortal said the social network recently teamed up with RiskIQ to fend off other potential malvertising threats.

Cybercriminals aren’t standing still, of course. Just a few weeks ago, Threatpost said a group of hackers were combining malvertising with ransomware using the Magnitude exploit kit. Much like the best legitimate advertising, these kinds of threats will be increasingly difficult to ignore.