In late August, the FBI took down and dismantled Quakbot, a banking Trojan that primarily spread through spam and phishing emails and has been active and continuously updated since 2008.
Trustwave SpiderLabs has tracked Qakbot for years and has worked hard to counter the malware’s efforts, including publicly releasing the encryption algorithm Qakbot used to encrypt registry keys, enabling victims to recover from an attack.
The multinational effort against Qakbot included the U.S., France, Germany, the Netherlands, Romania, Latvia, and the United Kingdom, represents one of the largest U.S.-led disruptions of a botnet infrastructure used by cybercriminals to commit ransomware, financial fraud, and other cyber-enabled criminal activity, the FBI said in a statement.
Attackers such as REvil and LockBit have used Qakbot malware to facilitate ransomware attacks and other cybercrimes, causing hundreds of millions of dollars in losses to individuals and businesses in the U.S. and abroad. As part of the operation, the FBI gained lawful access to Qakbot’s infrastructure and identified over 700,000 infected computers worldwide—including more than 200,000 infected machines in the U.S., the FBI reported.
According to the FBI, it was able to take action against Qakbot by first gaining lawful access to Qakbot’s infrastructure and identified over 700,000 infected computers worldwide—including more than 200,000 in the U.S.
To disrupt the botnet, the FBI redirected Qakbot traffic to Bureau-controlled servers that instructed infected computers to download an uninstaller file. This uninstaller—created to remove the Qakbot malware—untethered infected computers from the botnet and prevented the installation of any additional malware.
“All of this was made possible by the dedicated work of FBI Los Angeles, our Cyber Division at FBI Headquarters, and our partners, both here at home and overseas,” said FBI Director Christopher Wray. “The cyber threat facing our nation is growing more dangerous and complex every day. But our success proves that our own network and our own capabilities are more powerful.”
Spiderlabs detailed Qakbot’s recent activity in a series of blogs this year that explained how attackers spread the malware using malicious PDF, HTML, and OneNote attachments, with the threat actors shifting their methodology as security teams devised defenses.
Qakbot’s evolution and ability to adapt has enabled it to evade detection and infect victims. Right after Microsoft blocked malicious file embedding in OneNote, Qakbot operators shifted to using PDFs with embedded malicious links to deliver their payloads.
SpiderLabs spotted OneNote attachments being used in December 2022, with the team noting Qakbot was the primary malware being distributed using multiple downloading techniques, predominantly PowerShell or MSHTA, as the initial payload delivery.
When it came to using PDFs, SpiderLabs noted attackers designed the PDF document to look like an Adobe Acrobat or Microsoft Azure update panel. The text lures the users into clicking the button to view the document, but once clicked, it will download an intermediate file like an archive or scripts that will eventually lead to the download of the Qakbot DLL. There’s a variant where the embedded link drops a password-protected archive, and the password is included in the maliciously crafted PDF.
Qakbot started using HTML smuggling in June 2022. It shifted from macro documents to HTML as Microsoft pushed restrictions on using macros from the Internet.
A Qakbot email campaign from September 2022 showed the attacker using a plain template and did not impersonate well-known brands. Instead, the malware tricks the user into clicking the HTML attachment, which causes an encrypted ZIP archive to be saved to disk. The email and the HTML attachment contain the password to extract the ZIP content.