Number:IRCNE2014042145
Date: 2014-04-04
According to “computerworld”, attackers exploited a vulnerability in a popular video-sharing site to hijack users' browsers for use in a large-scale distributed denial-of-service attack, according to researchers from Web security firm Incapsula.
The attack happened Wednesday and was the result of a persistent cross-site scripting (XSS) vulnerability in a website that Incapsula declined to name, but said is among the top 50 websites in the world by traffic based on statistics from Amazon-owned firm Alexa.
XSS flaws are the result of improper filtering of user input and can allow attackers to inject unauthorized script code into Web pages. If the code is stored permanently by the server and delivered to all users who view the affected page, the attack is considered persistent.
Users of the unnamed video-sharing site can create profiles and leave comments and the XSS flaw allowed attackers to create a new account with rogue JavaScript code injected into the img tag corresponding to its profile picture.
"As a result, every time the image was used on one of the the site's pages (e.g., in the comment section), the malicious code was also embedded inside, waiting to be executed by every future visitor to that page," the Incapsula researchers said Thursday in a blog post.
The rogue code generated an iframe that loaded a DDoS script into visitors' browsers from a third-party command-and-control (C&C) server, effectively hijacking the browsers and forcing them to send requests in the background to a third-party site.
The resulting attack against the targeted site consisted of 20 million GET requests received from 22,000 browsers at a rate of around 20,000 requests per second, according to the Incapsula researchers.
Exploiting XSS vulnerabilities to launch DDoS attacks is not something new. The technique itself has been known for years, but hasn't been used frequently because it requires vulnerabilities in highly trafficked websites to be truly effective.
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