You wouldn't expect to encounter password-stealing malware while browsing Facebook, but hackers are now targeting vulnerable Windows PCs on the popular social network with fake ads.

As reported by BleepingComputer, security researchers at Trustwave lured unsuspecting Facebook users into clicking on malicious ads with fake Windows themes and fake downloads of pirated games and software We have discovered several new campaigns. This is done either by creating a new Facebook business account or by hijacking an existing one.

Here is what you need to know about these new campaigns and how to protect your own Windows PC from malware.

Trustwave reports that the hackers behind this latest attack are bringing out thousands of ads per individual campaign. For example, the top campaign called “blue-softs” had 8,100 ads, while “xtaskbar-themes” had 4,300.

Upon clicking on these fake ads, potential victims are directed to malicious sites hosted on Google Sites and True Hosting, which appear to be download pages for themes and software promoted on Facebook. These sites have a download button that, when clicked, downloads a ZIP file with the same name as the product advertised online.

As you might imagine, these ZIP files actually contain the SYS01 information-stealing malware first discovered by the cybersecurity firm Morphisec in 2022. The malware itself uses a collection of executables, dynamic link library (DLL) files, PowerShell scripts, and PHP scripts to install itself and steal data from targeted Windows PCs.

SYS01 steals cookies from browsers and steals passwords and the victim's browsing history stored therein. However, it also includes the task of leveraging Facebook cookies on infected devices and extracting data from the victim's profile, including name, email, and birthday on the social network.

Even if you do not use Facebook, you should be aware that Trustwave has identified similar fraudulent ad campaigns on both YouTube and LinkedIn.

The first and most important thing to do to avoid falling victim to this and similar campaigns is to not click on the ads.

Hackers can buy ad space just as easily as legitimate companies, so it is best not to click on any ads at all to stay safe. In fact, the FBI even recommends the use of ad blockers.

Nevertheless, if you see an ad for something you like, you should head to a search engine or, better yet, go directly to the company's site and purchase the product you might be interested in. If you need to interact with ads online, you are going to want to make sure you are using the best antivirus software to protect yourself from malware and other viruses that the ads may be spreading.

We have seen fake ads on both Google and Facebook, and both companies are trying to crack down on this practice. Until then, we need to be careful where we click and avoid downloading anything from unfamiliar sites or sources online.