QBot malware, previously known as QakBot, has evolved from a banking Trojan to a malware that provides initial access to corporate networks for other threat actors.
QBot drops additional payloads such as Cobalt Strike, Brute Ratel, and other malware that allow other threat actors to access the compromised device, spread laterally through a network, steal data, and eventually deploy ransomware in extortion attacks.
Recently, security researchers have been tracking QBot’s use of a new email distribution method. QBot is being distributed through reply-chain phishing emails, where threat actors use stolen email exchanges and reply to them with links to malware or malicious attachments.
The phishing emails use a variety of languages, making this a worldwide malware distribution campaign. Attached to these emails is a PDF file named ‘CancelationLetter-[number].pdf,’ which, when opened, displays a message stating that it contains protected files, and to display them, click on the “open” button.
However, clicking on the button downloads a ZIP file that contains a Windows Script File (WSF). The WSF file is heavily obfuscated, with the ultimate goal of executing a PowerShell script on the computer.
The PowerShell script attempts to download a DLL from a list of URLs. When the QBot DLL is executed, it runs the PING command to determine if there is an internet connection. The malware then injects itself into the legitimate Windows wermgr.exe (Windows Error Manager) program, where it runs quietly in the background.
QBot malware infections can lead to devastating attacks on corporate networks, making it vital to understand how the malware is being distributed.
Ransomware affiliates linked to multiple Ransomware-as-a-Service (RaaS) operations, including BlackBasta, REvil, PwndLocker, Egregor, ProLock, and MegaCortex, have used QBot for initial access into corporate networks. Researchers have shown that it only takes around 30 minutes for QBot to steal sensitive data after the initial infection.
Even worse, malicious activity only takes an hour to spread to adjacent workstations. Therefore, if a device becomes infected with QBot, it is critical to take the system offline as soon as possible and perform a complete evaluation of the network for unusual behavior.
