What is "malvertising"

n. Internet advertising whose real intention is to deliver malware to the PC when the ad is clicked.

Malvertising (a portmanteau of "malicious advertising") is the use of online advertising to spread malware.

Malvertising involves injecting malicious or malware-laden advertisements into legitimate online advertising networks and webpages. Online advertisements provide a solid platform for spreading malware because significant effort is put into them in order to attract users and sell or advertise the product. Because advertising content can be inserted into high-profile and reputable websites, malvertising provides malefactors an opportunity to push their attacks to web users who might not otherwise see the ads, due to firewalls, more safety precautions, or the like. Malvertising is "attractive to attackers because they 'can be easily spread across a large number of legitimate websites without directly compromising those websites'."

Malvertising is a fairly new concept for spreading malware and is even harder to combat because it can work its way into a webpage and spread through a system unknowingly: "The interesting thing about infections delivered through malvertising is that it does not require any user action (like clicking) to compromise the system and it does not exploit any vulnerabilities on the website or the server it is hosted from... infections delivered through malvertising silently travel through Web page advertisements." It is able to expose millions of users to malware, even the most cautious, and is growing rapidly: "In 2012, it was estimated nearly 10 billion ad impressions were compromised by malvertising." Attackers have a very wide reach and are able to deliver these attacks easily through advertisement networks. Companies and websites have had difficulty diminishing the number of malvertising attacks, which "suggests that this attack vector isn’t likely to disappear soon."