Isn’t it neat to find out about new services and discounts without raising a finger to look them up? Ads on the web have become essential tools for companies to promote their products, and for people to learn about bargains. But they’ve also caught the attention of cybercriminals who increasingly use them as virus and spyware-spreading channels. Their goal? Damage your data, steal your personal details or even control your computer remotely. This is when useful ads go malicious and harmful, and are referred to by specialists as “malvertisements”.
Good ads gone malicious
There are two common methods used by cybercriminals to spread viruses and other malware through ads on the Internet. One entails criminals acting as trustworthy companies. They place a series of “clean” ads on trusted sites that host third-party ads, and leave them running for some time to gain a “good reputation”. Then, they attack – they insert a virus or spyware in the code behind the ad, and after a mass virus infection is produced, they remove the virus. In this case, because the ad network infrastructure is very complex with many linked connections between ads and click-through destinations, the criminals’ identity can hardly be traced.
Another common way for criminals to turn legitimate ads into malicious ads is by hacking trusted sites and injecting viruses into banner ads. Usually, the next day – after the harm’s been done – they’re gone.
These types of malvertisements can take the form of Google ads, pop-ups, antivirus notifications etc.
How does malvertising work?
Once the malicious ad is put into place, a proper malvertising campaign starts running, targeting millions of Internet users who access the respective sites. The user clicks on the ad to visit the advertised site, and instead is directly infected or redirected to a malicious site. These sites trick users into copying viruses or spyware usually disguised as Flash files, which are very popular on the web.
Thus, users’ trust is a very important factor in making malvertising campaigns successful. Examples of trustworthy sites that have been hacked and used by cybercriminals to insert viruses in the ads are those of The London Stock Exchange and The New York Times.
What can I do to avoid virus infections contracted from malvertising?
- Don’t be too trusting! If, say, a random pop-up appears on your screen saying you’re the one hundredth visitor and you won something huge (free), chances are that’s a malicious ad, and the only thing you can win by clicking it is a virus. Also, do not trust pop-up online surveys. Long story short, avoid such ads.
- Be extra careful during weekends! Malvertising campaigns are usually triggered over weekends, when IT resources are low and attacks are less likely to be noticed. Make sure you have effective antivirus protection that includes “safe browsing” functionality, so that with each site you visit, you’re notified whether it’s safe to access it or not. BullGuard Antivirus contains a feature like that.
- Update, update, update! Out-dated software on your computer (browsers and other applications installed on your PC) makes you more vulnerable to hackers and viruses. And due to the fast evolution of malvertising methods, it’s always best to have a vulnerability scanner to check your system for out-of-date software and update it.
- Prevent, rather than cure! While you can’t always figure out which ads are, in fact, malvertisements, you can lower the chances of getting infected by installing comprehensive internet security software. BullGuard Internet Security 12 is, in this respect, a great solution to all internet security problems – including malicious ads that run amok –, as it comes with the broadest selection of internet security features on the market.