What is Malvertising? How to Avoid it?

There are many methods being used to compromise users of the Internet, so that their information can be obtained by cyber-criminals. Once a computer is compromised, the cyber-criminals can use the users data for anything they want. Such events may even result in Identity Theft, where cyber-criminals use your identity for taking loans, etc. and leave you in a mess. Among the many newer methods of compromising a computer is –  Malvertising. Let us take a look at what is malvertising and how to stay safe by avoiding it.

What is Malvertising

Malvertising or Maladvertising contains two words: Malicious + Advertising. This is not just about malicious misleading advertisements that lure users to Phishing websites. Malvertising is about compromising your computer, by downloading a short malicious code on to it, when you hover on or click on an advertisement. Some adverts will even download malicious code to your computer, while the website is still loading in the background. In such cases, by simply visiting a website, users can get infected via Drive-by-downloads.

Cybercriminals are using advertisements as a means to hack in to your computers. Since these advertisements look genuine, users click on them expecting to be taken to a website, where they can get more information about the advert. However, instead of being redirected, the click action triggers a download of a small but malicious code to users’ computers. In fact the infection can even take place silently in the background, even as the ad is being loaded by the browser. Since the ad networks serving these ads are pretty huge, it is nearly impossible to identify the person or organization behind the malicious advertisement. Many popular websites too end up unknowingly serving such adverts without any harmful intent, as they do not know that the adverts are malicious.

How Does Malvertising Work

One does not need to hack a website to place malicious advertisements on that website. Instead, criminals use advertising networks to insert their advertisements on thousands of millions of websites. If you know how advertising on the Internet works, you know that once an ad is submitted, after scrutiny, it is pushed into the Internet where it appears on websites related to the keywords typed by users for any kind of information.

Cyber-criminals use display advertising to distribute malware. Possible vectors of attack include malicious code hidden within an ad creative (such as a swf file), executables embedded on a webpage, or bundled within software downloads. All web publishers and websites are potential targets for malware authors attempting to spread their software by hiding malicious code within an ad’s SWF (Flash) file, GIF file or landing page.

If an advertiser or agency provides you with an infected ad, your computer and personal information, and that of your site’s visitors, can be exposed to serious harm. Google’s Anti-Malvertising.com website has a few tips ad publishers and website owners may want to check out.

Although reputed advertising networks do scrutinize the ads for the obvious factors, like banned words, prohibited products, etc., without a proper scrutiny of the code, malvertisements can slip through! In such a scenario, the ad network places millions of users at risk by displaying the infectious advertisements on various websites. And there are yet other ad networks who may even ignore such malvertising, for the lure of good money.

In other cases, criminals claim to represent genuine institutions, submit clean adverts directly to the websites instead of ad networks. Later, they attach a malicious code to the advert that is downloaded to computers of users who click on the adverts on websites. After a while, when the target is met, the criminals remove the code. The advert stays there for the contract period. Between attaching and removing the code, the criminals get to hack plenty of computers and thus, much information about different Internet users is at their hands. They can use this information for any purpose they like.

How To Avoid Malvertising

Precaution is the only key to avoid malvertising. Malicious ads can appear even on reputed websites. If any ad looks overtly promising, simply avoid them. For example, popups saying you are the 100th visitor and are chosen for a prize – ignore it. Avoid anything that promises you likes of money, gifts, discount coupons etc. for free. Since the advertisements that appear on the websites are result of network advertisers, it is up to them to check the advertisements for malicious codes. Most of them just check the language profanity and publish the ads. These days, most reputed networks like the Google AdSense network check the entire code, but there have still been the rare case, where malicious advertisements have crept in.

There are some cloud-based malvertising detection platforms and solutions, which deliver insight about and control over the safety of online ads being served on the websites. Large publishers may want to check this option out. As a user, make sure you have a good security software and inculcate safe browsing habits. And remember to keep your operating system and your installed software, including browser plugins, always updated.

Some recent examples of Malvertising

Certain ads on DeviantART.com were redirecting users to the Optimum Installer web page in order to install Potentially Unwanted Applications on unsuspecting users. Hackers had compromised Clicksor Ad Network to distribute malware. Blackhole Exploit kits were being distributed via the Clicksor Ad Network and others. In yet another very recent case, Java exploits were being served via advertisements on Java.com, reported Fox IT.com.

Infographic This Infographic shows how Malvertising works.

what is malvertising

It is therefore important that publishers use only such advertising networks and exchanges that have strong screening methods and who take immediate action, once instances of Malvertisements are found, in order to prevent the spread of malware within their systems, as well as contain the damage which may be caused.

Bad, vulnerable and insecure plugins often get compromised. So as I mentioned earlier, make sure you have a good security software and inculcate safe browsing habits. And remember to keep your operating system and your installed software, including browser plugins, always updated.

Stay safe!

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Anand Khanse is the Admin of TheWindowsClub.com, a 10-year Microsoft MVP Awardee in Windows & a Windows Insider MVP. Please read the entire post & the comments first, create a System Restore Point before making any changes to your system & be careful about any 3rd-party offers while installing freeware.