Google’s JavaScript Ban Boosts SVG Image Misuse

January 31, 2017 @ 1:30 PM
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2 min read

This year, Google has been implementing many previously announced security policies, one of which involves the scalable vector graphics (SVG) image format.

In addition to becoming its own root certificate authority to bypass issuance problems, Google plans to ban all JavaScript (JS) attachments in its Gmail email service as of Feb. 13, The Inquirer reported. The technology giant will cease to blindly trust .zip attachments that resolve into JS files, since cybercriminals have long disseminated malware this way.

Cybercriminals Respond With SVG Image Attacks

Malware authors will surely find new ways to attach harmful JS files to emails. In fact, they may have already zeroed in on a delivery method that first appeared in a spam campaign last November targeting Facebook users in France, according to Bleeping Computer.

An SVG image file usually contains graphical data, but it can also run any embedded JS present in the file. The poisoned SVG file used in the Facebook attack redirected victims’ browsers to a fake website designed to steal login credentials.

SVG images work by default with Internet Explorer (IE). IE has proven to be wide open to JS-based exploitation, so it is no surprise that the browser can be easily directed to a malware-controlled site.

SVG Image Attacks Surge

Another Bleeping Computer article reported that security firms have detected an uptick in SVG image attacks in the past few weeks. In a recent campaign, for example, Japanese targets received legitimate-looking, seemingly business-oriented emails that contained .zip attachments.

These attachments opened malicious SVG files designed to launch a page that prompted victims to download an .exe file. If downloaded and opened, the file installed the Ursnif Trojan. While the SVG file did not specifically conduct the attack, it explicitly facilitated one.

Consider Following Google’s Lead

As a data structure, an SVG file is general enough to allow for additional features beyond its core graphical functions. This flexibility, however, comes at the expense of security.

Unless there is a definite, demonstrable need, security professionals should consider banning SVG files in routine cases. When Google’s JS ban takes effect, malware authors will likely turn to SVG image-based attacks.

Larry Loeb
Principal, PBC Enterprises

Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE mag...
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