Rogue copies of Green Simurgh, an Internet proxy software application used in Iran and Syria, have been found to contain malware that records users' activities and keystrokes.
Green Simurgh is an anti-censorship application that routes a computer's outbound connections to a server located in the U.S. This allows the software's users to bypass network filters and access Internet resources that would normally be banned by their ISP.
Green Simurgh doesn't require any installation and can run directly from USB memory sticks, which makes it suitable for users who access the Internet from cafes and public computers.
The software has been used in Iran since 2009 and, according to the Citizen Lab, a University of Toronto laboratory that researches digital media, global security and human rights, Syrian users have also began to rely on it.
"It has recently come to our attention that this software is being recommended and circulated among Syrian Internet users for bypassing censorship in their country," said Citizen Lab technical adviser Morgan Marquis-Boire in a blog post on Friday. "This information led to the discovery and analysis of a back-doored version of this software."
The malicious version is being distributed from file sharing websites like 4shared.com as a package called Simurgh-setup.zip. The archive contains an executable file that masquerades as a Green Simurgh installer.
When run on a Windows machine, the rogue installer drops a legitimate copy of the Green Simurgh software in the Program Files directory, but also installs a computer Trojan horse that runs in the background.
"[The Trojan horse] keeps a log of your username, machine name, every window clicked and keystroke entered," said Chester Wisniewski, a senior security adviser at antivirus vendor Sophos, in a blog post on Tuesday. "It attempts to submit these logs to some servers located in the United States, but registered to an entity that appears to be based in Saudi Arabia."
Considering that thousands of users depend on the legitimate Simurgh software, it's likely that a lot more people have been impacted by this malware than by Flame -- a recently discovered cyberespionage threat that has received a lot of attention in the media -- Wisniewski said.
"Unlike Flame, which is a highly targeted malware that has only been found on a handful of computers globally, this malware is targeting users for whom having their communications compromised could result in imprisonment or worse," he said.
The Green Simurgh developers have posted a warning on their website, urging users to only download the proxy software from the official download page and to verify the MD5 checksums of the package before running it. They also advised users who believe that they might have been infected with this malware to run an up-to-date antivirus scanner in order remove it from their computers.