Sefnit click fraud malware drops Tor for SSH, Facebook researchers say

The malware program that flooded the Tor network with new clients last year is back, but now uses SSH for command and control

Security researchers from Facebook have identified a new variant of the Sefnit click fraud malware program that uses SSH for command and control instead of the Tor anonymity network.

The threat, which is also known as Mevade, infected millions of computers last year and caused a sudden spike in Tor usage.

Sefnit is a family of malware programs that has been used to defraud advertisers by generating rogue ad clicks since at least 2011, according to an analysis in September by researchers from the Microsoft Malware Protection Center.

In mid-August, a Sefnit variant called Mevade caused the number of daily users on the Tor anonymity network to rise from around 500,000 to over 3 million because it used a Tor Hidden Service -- a website accessible only from inside the Tor network -- as a command-and-control (C&C) server.

Unlike older Sefnit variants that hijacked user clicks on search results, Mevade used a different click fraud technique that involved transforming infected computers into proxies for routing fraudulent ad click traffic.

It's not clear how well Tor worked as a C&C channel for Mevade's authors given that traffic over the anonymity network can be slow, especially when overcrowded with clients. Poor performance might explain why a new version of Sefnit recently analyzed by researchers at Facebook no longer relies on Tor.

Instead, the new variant uses the Plink (PuTTY link) command-line network connection tool to access C&C servers over the SSH (Secure Shell) protocol, the Facebook Security Team said Monday in a blog post that contains details about the new threat.

The use of Plink further indicates that Sefnit's authors have a tendency to repurpose legitimate software for their goals. This behavior was previously observed with Tor and 3proxy, a free proxy server program.

"This post references additional files, domains and artifacts, including the SSH functionality in channel.dll," the Facebook researchers said. "We hope these details and indicators help security teams audit their assets for signs of Sefnit."

Read more: Purple WiFi partners with Wavelink

Join the newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection

Tags online safetyMicrosoftsecuritymalwareFacebook

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Lucian Constantin

IDG News Service
Show Comments

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Ratchada Dunn

Sharp PN-40TC1 Huddle Board

The Huddle Board’s built in program; Sharp Touch Viewing software allows us to easily manipulate and edit our documents (jpegs and PDFs) all at the same time on the dashboard.

George Khoury

Sharp PN-40TC1 Huddle Board

The biggest perks for me would be that it comes with easy to use and comprehensive programs that make the collaboration process a whole lot more intuitive and organic

David Coyle

Brother PocketJet PJ-773 A4 Portable Thermal Printer

I rate the printer as a 5 out of 5 stars as it has been able to fit seamlessly into my busy and mobile lifestyle.

Kurt Hegetschweiler

Brother PocketJet PJ-773 A4 Portable Thermal Printer

It’s perfect for mobile workers. Just take it out — it’s small enough to sit anywhere — turn it on, load a sheet of paper, and start printing.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?