BLACK HAT - Blog readers vulnerable to embedded malware

Reading blogs could cause your computer to catch a virtual cold, said a leading security expert Wednesday at the Black Hat USA conference.

Internet users who employ Web-based services such as Bloglines or Web browsers such as Firefox to read Web site feeds and blogs are vulnerable to embedded malicious code that can install spyware, log users' passwords, scan PCs and corporate networks for open ports and more, said Caleb Sima, chief technology officer at SPI Dynamics, a Web application security company.

So far, only a few proof-of-concept attacks against blog readers from Google and Yahoo have occurred, Sima said, though he believes that more are on the way.

"The only reason we haven't had a lot of problems yet is because no one has really thought of it," he said. According to Sima, software and services used to download feeds transmitted via the RSS or Atom formats can unwittingly download and execute JavaScript code buried within the text.

JavaScript is a scripting programming language that has become popular as a way of providing rich interactivity to Web sites. But it can also be employed by hackers to take over users' computers, sniff for vulnerabilities and more.

"The possibilities are limited only by how creative you are," Sima said, who calls the technique "feed injection." Sima said this type of attack is a variant of cross-site scripting, a popular way of attacking Web sites by entering HTML or JavaScript commands instead of text, which can cause errors and disable the site, leaving it open to hackers.

Seemingly random strings of characters such as "

This way, seemingly garbled text can hide malicious JavaScript commands that can do damage without having to install or run an outside file, a telltale sign that would normally alert an antivirus or antispyware program.

But don't users sign up for RSS feeds only from Web publishers they already know and trust? True, said Sima, but there are many ways those publishers could be compromised. A Web feed could contain a link to another Web site or blog that's hosting malicious JavaScript. Or the Web feed's author could unknowingly paste that JavaScript into his own blog. Or a blog may have an area allowing readers to post public comments. Those can also store malicious bits of JavaScript, Sima said.

Finally, because RSS and Atom readers don't typically authenticate the publisher of each feed every time they download, they might blindly download feeds sent by an impersonating or infected Web publisher, Sima said.

Because RSS and Atom feeds are normally stored by blog readers as HTML files on users' local hard drives, they also bypass Web browser security settings that might be set to prevent JavaScript from unknown outside Web sites from executing. Turning off JavaScript altogether to prevent such attacks is no solution, Sima said. Too many popular Web sites and applications today rely on JavaScript invisibly executing in the background to operate, making them "painful to use." The best way to guard against these sorts of attacks, he said, would be for blog-reading software and services to re-encode all JavaScript it receives to render it harmless.

"It could be as simple as adding a few lines of extra code," he said. Creating this filter would not cause feeds to arrive much slower, either, he said. But as far as he knows, no blog-reading software or service re-encodes the JavaScript as he suggests to de-fang it.

In the absence of blog readers filtering their feeds, Sima recommends that CIOs and chief information security officers start treating individual PCs as potential attack points.

Join the newsletter!


Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Eric Lai

Show Comments

Cool Tech

Toys for Boys

Skywatcher Dobsonian 8″ Collapsible Telescope

Learn more >

Family Friendly

Whodunnit™ Duo-Scope MFL-007 Microscope Kit

Learn more >

Stocking Stuffer

Logitech Ultimate Ears Wonderboom 2 Bluetooth Speaker

Learn more >

Christmas Gift Guide

Click for more ›

Brand Post

Most Popular Reviews

Latest Articles


PCW Evaluation Team

Tom Sellers


This smart laptop was enjoyable to use and great to work on – creating content was super simple.

Lolita Wang


It really doesn’t get more “gaming laptop” than this.

Jack Jeffries


As the Maserati or BMW of laptops, it would fit perfectly in the hands of a professional needing firepower under the hood, sophistication and class on the surface, and gaming prowess (sports mode if you will) in between.

Taylor Carr


The MSI PS63 is an amazing laptop and I would definitely consider buying one in the future.

Christopher Low

Brother RJ-4230B

This small mobile printer is exactly what I need for invoicing and other jobs such as sending fellow tradesman details or step-by-step instructions that I can easily print off from my phone or the Web.

Aysha Strobbe

Microsoft Office 365/HP Spectre x360

Microsoft Office continues to make a student’s life that little bit easier by offering reliable, easy to use, time-saving functionality, while continuing to develop new features that further enhance what is already a formidable collection of applications

Featured Content

Product Launch Showcase

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?