A new version of the TDL rootkit-type malware program downloads and abuses an open-source library called the Chromium Embedded Framework that allows developers to embed the Chromium Web rendering engine inside their own applications, according to security researchers from antivirus vendor Symantec.
In an effort to temporarily block the abuse, CEF project administrators suspended the framework's primary download location on Google Code.
The TDL malware generates profit for its authors by redirecting the victims' search results to websites and services of a dubious nature, by displaying pop-up advertisements for various products and services or by infecting computers with other threats as part of a pay-per-install malware distribution scheme.
The latest TDL variant no longer uses custom code to implement its Web browser functionality, and instead relies on CEF, which it downloads from the project's site on Google Code. This allows the malware to have smaller components that are easier to update, the Symantec researchers said Friday in a blog post.
CEF allows developers to build applications that can display Web pages inside of their own windows by rendering the HTML and JavaScript code with the Chromium browser engine. "The host application can optionally control resource loading, navigation, context menus, printing and more, while taking advantage of the same performance and HTML5 technologies available in the Google Chrome Web browser," the CEF developers say on the project's website.
After learning that the CEF library is being abused by malware, the CEF creators decided to block automated downloads of their software by implementing CAPTCHA and session verification. However, since this couldn't be done on Google Code, they had to move their file downloads to a third-party site.
"It has come to our attention that a CEF binary release file (zip archive) hosted on our project page was being directly downloaded by a distributed malware product for illegal purposes," they wrote in a notice posted on the project's official site on Google Code. "The Chromium Embedded Framework (CEF) project and its authors do not condone or promote the use of the CEF framework for illegal or illicit purposes. We will take all actions reasonably within our power to frustrate this use case. For that reason current and future downloads will be hosted externally at http://www.magpcss.net/cef_downloads/. This new download location offers improved features and protections over those offered by Google Code hosting."
This news prompted one CEF user to ask on the project forum if there's any risk of antivirus products flagging CEF as malware because of the abuse.
"Given the large number of companies currently using libcef for legitimate purposes I think it's unlikely that we'll end up on any anti-virus black lists," said Marshall Greenblatt, the CEF lead developer, in response to the question. However, companies that bundle CEF with their applications are encouraged to digitally sign the binary files before distribution, he said.
