Malware appearing in Google's Play Store apps isn’t something new, but a newly discovered piece of code proved to be particularly unpleasant. Among the different ways that ‘Adult Swine’ affects users is by displaying porn ads within games, and many of the titles it appeared in were aimed at children.

Google has removed 60 games from its Play Store after security firm Check Point uncovered the malware. Its ads come from main providers, who don’t allow their content to be used this way, and from the malware’s own ad libraries, which are the source of the pornographic and inappropriate adverts. Back in November, at least one parent left a review complaining that his four-year-old son was exposed to the ads.

Some of the ads use scareware pop-ups that warn users they’ve been infected with a virus. Clicking on the link to remove it directs them to “questionable” security apps within the Google Play Store, which could cause even more problems if installed.

Another element of Adult Swine is tricking victims into signing up to premium services and charging their accounts. It does this through another popup that claims users can win an iPhone by answering some simple questions. If someone completes the quiz, they’re asked to enter their phone number to receive the prize, but the information is really used to register for a premium service.

While most people will know not to click on the ads or hand over any data, they could have fooled less tech-savvy users and children.

Google Play’s data shows apps containing the code were downloaded between 3 million and 7 million times. They included Five Nights Survival Craft, which was downloaded a minimum of one million times; McQueen Car Racing Game, based on characters from Disney Pixar’s Cars, and Addon Pixelmon for MCPE.

Google has now removed the offending apps. “We’ve removed the apps from Play, disabled the developers’ accounts, and will continue to show strong warnings to anyone that has installed them. We appreciate Check Point’s work to help keep users safe,” the company said, in a statement to the Financial Times.