Malvertising 101

In addition to ransomware, another important cyber threat for small to midsize businesses to be aware of is malvertising, or malicious advertising. In this post, we’ll take a deeper dive into the basics of malvertising and answer common questions, such as:

  • What is malvertising?
  • How does malvertising work?
  • How can I avoid malvertising?

What is malvertising?

Malvertising is the use of online, malicious advertisements to spread malware and compromise systems. Generally this occurs through the injection of malicious code into online advertisements on legitimate online advertising networks like The New York Times Online, The London Stock Exchange and even Spotify, all of which have been exposed to malvertising in recent years. Cybercriminals then pay the online advertising networks to display the infected ads on various websites, exposing every user visiting these sites to the potential risk of infection.

How does malvertising work?

Generally, the legitimate advertising networks and websites are not aware they are serving malicious content. Each day, a large number of ads are submitted to the various advertising networks, making it very difficult for the advertising networks to perform a thorough analysis of each ad. Often advertisers work on a complaint based system, wherein if a complaint is lodged against an ad or ads from a specific group, a deep analysis is then performed at that time. Many websites, especially large ones with several hundred thousand users per day, rely on third party vendors and software in order to display its ads, and this automation makes online ads increasingly vulnerable to malvertising. In addition, it is very difficult for cybersecurity experts to identify exactly which ad is malicious because the ads on a web page constantly change. This means that one visitor may be infected, but the next ten, who visit the exact same web page, won’t be infected.

When a user clicks on a malicious ad, one or more of the following can happen:

  • Code will execute that installs malware or adware on the user’s computer
  • The user is redirected to a malicious website instead of the target suggested by the ad’s content
  • The user is redirected to a malicious website very similar to the real site, which is operated by the attacker (phishing)

How can I avoid malvertising?

Malvertising can be difficult to detect and mitigate and requires action by end users. End users can help mitigate malvertising by:

  • Using strong antivirus software meant for businesses, such as TrendMicro
  • Using ad blockers to block all ads, including those with malicious elements
  • Avoiding the use of Adobe Flash and Oracle Java whenever possible, as they are commonly exploited by malvertising
  • Keeping browsers and plugins up-to-date

To combat malvertising and other cyber threats, businesses of all sizes should invest wisely in solutions that continuously discover and patch security vulnerabilities. We also recommend businesses invest more in their people, including training and certification for IT security personnel and ongoing security awareness training for all employees. Never underestimate the value of your human firewall! For the best in today’s data security solutions, contact Simplify Tech!


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