Microsoft patches Windows zero-day used to drop ransomware
Microsoft has fixed a security vulnerability used by threat actors to circumvent the Windows SmartScreen security feature and deliver Magniber ransomware and Qbot malware payloads.
“An attacker can craft a malicious file that would evade Mark of the Web (MOTW) defenses, resulting in a limited loss of integrity and availability of security features such as Protected View in Microsoft Office, which rely on MOTW tagging,” Redmond explained on Tuesday.
According to Microsoft, this security flaw can only be exploited using three attack vectors:
- In a web-based attack scenario, an attacker could host a malicious website that exploits the security feature bypass.
- In an email or instant message attack scenario, the attacker could send the targeted user a specially crafted .url file to exploit the bypass.
- Compromised websites or websites that accept or host user-provided content could contain specially crafted content to exploit the security feature bypass.
However, in all these scenarios, the threat actors would have to trick their targets into opening malicious files or accessing attacker-controlled websites with CVE-2022-44698 exploits.
Microsoft released security updates to address this zero-day during the December 2022 Patch Tuesday after working on a fix for this actively exploited zero-day vulnerability since late October.
Exploited in malware attacks
This would cause SmartCheck to error out and allow the malicious files to execute without throwing any security warnings and install the Magniber ransomware, even though it got tagged with a MoTW flag.
Last month, the same Windows zero-day vulnerability was also abused in phishing attacks to drop the Qbot malware without displaying MOTW security warnings.
As security researcher ProxyLife found, threat actors behind this recent QBot phishing campaign switched to the Windows Mark of the Web zero-day by distributing JS files signed with the same malformed key used in the Magniber ransomware attacks.
QBot (aka Qakbot) is a Windows banking trojan that has evolved into a malware dropper that will steal emails for use in subsequent phishing attacks or deliver additional payloads such as Brute Ratel, Cobalt Strike, and other malware.
During the December 2022 Patch Tuesday, Microsoft also fixed a publicly disclosed zero-day (CVE-2022-44710) that would allow attackers to gain SYSTEM privileges on unpatched Windows 11 systems.
Original Posts: Microsoft patches Windows zero-day used to drop ransomware