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Antivirus vendor Trend Micro has recently detected a drive-by download attack on Facebook that used malicious advertisements to infect users with malware.

“We encountered an infection chain, wherein the user is led from a page within Facebook to a couple of ad sites, and then finally to a page that hosts exploits,” the company’s security researchers warned Tuesday. “When we traced the connection between the ad sites and Facebook, we found that the ad providers were affiliated with a certain Facebook application. We checked on the said app, and found that it is indeed, ad-supported.”

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“Malvertising” attacks are usually the result of lax background screening practices on behalf of advertising networks or ad sale teams. Attackers usually impersonate legitimate advertisers in order to get their ads approved and later swap them with malicious code.

A lot of popular web sites and big ad networks have fallen victim to such attacks over the years. Facebook also dealt with this form of abuse in the past, but in those cases the ads were used to display fake security alerts that led to scareware.

However, malvertisements that bundle drive-by download exploits for vulnerabilities in popular browser plug-ins, or even the browser itself, are much more dangerous since they don’t require any user interaction.

In this case, users were directed to a page that loaded Java and ActiveX exploits, but while the attacked ActiveX vulnerability was patched in 2006, the Java ones were more recent, dating from 2010.

Facebook is usually plagued by other types of attacks. Trend Micro’s research identified the three most common threats on Facebook: “likejacking,” where users are tricked into posting a status update for a page they didn’t actually intend to give a “like” to, rogue applications, and spam campaigns.

Unfortunately, the design of Facebook’s platform, where thousands of third-party app developers can work with whichever advertisers they wish, favours malvertising. There’s not much Facebook can do about it, so the task of fending off such attacks ultimately falls with the users.

Statistics collected this year by security companies from live drive-by download toolkit installations show that Java exploits have the highest success rate, exceeding those of PDF or Flash exploits.

This is mainly because users do a poor job of updating the software, a lot of them not even knowing what Java is or that it’s installed on their systems. In fact, since there’s little Java content on the Web anymore, some security experts recommend that users should disable the plug-in from their browser if they don’t remember ever using it.

Keeping all software programs up to date, especially those that are accessible from the Web, is critically important for staying secure on the Internet. So is using an antivirus program capable of scanning Web traffic and detecting exploits.

Power users can resort to more advanced methods of protection such as the NoScript Firefox extension, which thanks to its opt-in approach to third-party scripts, blocks the majority of drive-by downloads, including those executed through malvertising.