Invalid traffic & fraud · also called Malicious advertising
Malvertising
Malvertising is using online ads to spread malware, scams or forced redirects, by sneaking harmful code or deceptive landing pages into ad creatives served through legitimate ad networks.
Malvertising turns an ad into a weapon. Attackers buy ad space like any advertiser, then use the creative, its code or its landing page to harm the people who see it: auto-redirecting phones to fake prize pages, triggering downloads of malware, impersonating banks or software brands, or pushing fake tech-support scams.
Because ads are served across thousands of reputable sites, malvertising can reach readers of trusted publishers without the publisher knowing. Attackers use cloaking to show harmless versions to ad reviewers and security scanners, and switch to the malicious version only for targeted users, devices or regions. Malvertising is related to, but not the same as, invalid traffic: its aim is usually to exploit people, although infected devices later feed botnets that commit ad fraud.
Defences include creative scanning by ad platforms and specialised vendors, blocking forced redirects in browsers, sandboxing ad frames, vetting new advertiser accounts, and industry efforts such as TAG's anti-malware programme. Publishers can also restrict which creatives and scripts may run in their ad slots.
Think of it like this
Malvertising is like a poisoned sweet slipped into a trusted shop's free-sample tray: customers trust the shop, so they take it without thinking.
An example
Readers of several news sites in Canada are redirected on mobile to a fake "you won a phone" page. Investigation traces it to a single ad creative that showed a clean image to scanners but ran redirect code on Android devices in certain regions.
Related terms
Cloaking
Cloaking is showing different content to ad reviewers, crawlers or verification tools than to real users, so a harmful, fraudulent or policy-breaking ad or site slips past checks.
Ad injection
Ad injection is inserting ads into websites without the site owner's permission, usually via browser extensions, adware or compromised networks, so a third party earns money from someone else's pages.
Botnet
A botnet is a network of computers, phones or smart devices infected with malware and remotely controlled by criminals, often used to generate fake ad impressions and clicks from real consumer devices.
Brand safety
Brand safety is the practice of keeping ads away from content that is harmful or universally unacceptable, such as terrorism, child abuse, hate speech or illegal activity, to protect an advertiser's reputation.
TAG (Trustworthy Accountability Group)
TAG (Trustworthy Accountability Group) is an advertising industry initiative, founded in 2014 by the ANA, 4A's and IAB, that runs certification programs against ad fraud, malware, piracy and for brand safety.
Sources: TAG: fighting malware, Google Advertising Policies: Abusing the ad network