When attackers use third-party ads to infect your computer with malware, it is called

When attackers used third party ads to infect your computer with malware, it is called MALVERTISING. 
Malvertising refers to the act of embedding malware in online advertisements. This is one of the means by which attackers infect users' system with virus. Malvertising involves incorporating malicious malware into legal advertisements from legal companies in order to hijack users computer system and spread malware.