Last updated on April 29, 2021.
If you pay attention to the world of security you’ve probably heard about the upswing in a type of attack known as Malvertising. Data Breach Today and Dark Reading recently featured articles on the subject. If you haven’t heard of it, Malvertising is the practice of inserting corrupted advertisements into trusted web sites, making them look just like any other ad that you may be enticed to click on. If you do click, you are redirected to a hosting site that will deliver some type of malware directly to your device, which could be ransomware, a bot client, traditional virus, or anything that would be of use for the attacker. Stopping this type of attack is more difficult than blocking traditional spam or email phishing attacks since the highly distributed nature of the Internet makes connections via advertisements to little-known or trusted domains very common.
Passive reliance on external parties such Google, ad vendors and agencies, industry groups, or government bodies isn’t the answer to solving this challenge. Malvertising isn’t going away. IT leaders need a solid strategy to deal with it by proactively identifying and blocking malicious ads as soon as they hit your network.
So what can you do? Perhaps the most significant impact a security team can have on this problem is to start paying attention to the types of domains being accessed by all the devices on the networks. DNS queries related to newly created domains, or those with low reputational scores should be disallowed by default, with exceptions made only after careful analysis. The next action should be to ensure that only devices on your network that actually need access to external resources have that access. For example, your IP-based security cameras probably don’t need to access an ad linked to eBay. Those devices should be limited to accessing the resources they need to do their job and nothing more. Finally, while you may not be able to prevent people from clicking on Malvertisements you should at least have the visibility into the actions of all devices on your network so that you can see when those devices start to exhibit changes in their behavior that may indicate some sort of compromise. Visibility is the foundation of detection, and early detection has become the key to success in the new world of security.
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