Operation Windigo: Malware used to attack over 500,000 computers daily after 25,000 UNIX servers hijacked by backdoor Trojan

Security researchers at ESET®, in collaboration with CERT-Bund, the Swedish National Infrastructure for Computing as well as other agencies, have uncovered a widespread cybercriminal campaign that has seized control of over 25,000 Unix servers worldwide.

The attack, which has been dubbed “Operation Windigo” by security experts, has resulted in infected servers sending out millions of spam emails. Its complex knot of sophisticated malware components are designed to hijack servers, infect the computers that visit them, and steal information.

Victims of “Operation Windigo” have included cPanel and kernel.org.

ESET’s security research team, which uncovered Windigo, published a detailed technical paper, presenting the findings of the team’s investigations and malware analysis. The paper also provides guidance on how to find out if your systems are affected and instructions for removing the malicious code.

OPERATION WINDIGO: Gathering Strength For Over Three Years

While some experts have spotted elements of the Windigo cybercriminal campaign, the sheer size and complexity of the operation has remained largely unrealised by the security community.

“Windigo has been gathering strength, largely unnoticed by the security community, for over two and a half years, and currently has 10,000 servers under its control,” said ESET New Business Development Director, Lee Bristow. “Over 35 million spam messages are being sent every day to innocent users’ accounts, clogging up inboxes and putting computer systems at risk. Worse still, each day over half a million computers are put at risk of infection, as they visit websites that have been poisoned by web server malware planted by Operation Windigo redirecting to malicious exploit kits and advertisements.”

Interestingly, although Windigo-affected websites attempt to infect visiting Windows computers with malware via an exploit kit, Mac users are typically served adverts for dating sites and iPhone owners are redirected to pornographic online content.

An Appeal To Sysadmins To Take Action Against Windigo

Over 60% of the world’s websites are running on Linux servers, and ESET researchers are calling on webmasters and system administrators to check their systems to see if they have been compromised.

How To Tell If Your Server Has Fallen Foul Of Windigo

ESET researchers, who named Windigo after a mythical creature from Algonquian Native American folklore because of its cannibalistic nature, are appealing for Unix system administrators and webmasters to run the following command which will tell them if their server is compromised or not:

$ ssh -G 2>&1 | grep -e illegal -e unknown > /dev/null && echo “System clean” || echo “System infected”

Tough Medicine For Windigo Victims

If sysadmins discover their systems are infected, they are advised to wipe affected computers and reinstall the operating system and software. It is essential that fresh passwords and private keys are used, as the existing credentials must be considered compromised.

For a higher level of protection in future, technology such as two-factor authentication should be considered.

Further Information

ESET has published a detailed investigation into the “Operation Windigo” cybercrime campaign, and the various malware components which make up the threat.

To download the full report, please visit welivesecurity.com/windigo.