Increase in Observations of Qakbot Malware 

THE THREAT

In the first week of April 2023, the eSentire Threat Intelligence team observed a significant increase in Qakbot incidents impacting various industries. Qakbot is an information-stealing malware. Qakbot is commonly delivered using phishing methods, including malicious emails from previously unseen email addresses or as replies to existing email conversations.   

In these incidents, Qakbot gained initial access through phishing emails containing a Zip archive containing a Windows script file (.wsf), a PDF document, or an HTML file using the HTML smuggling method. The malware can also retrieve CobaltStrike from a command-and-control site, and perform basic reconnaissance. However, observed attacks were isolated and alerted on, and the customers were notified for remediation.   

Qakbot is highly concerning as the malware has been observed leading to the delivery of multiple ransomware variants. eSentire is sharing details on these attacks, including indicators of compromise (IOCs), to increase awareness of this threat across our customers. 

What we’re doing about it

• eSentire MDR for Endpoint and Network have detections in place to identify Qakbot
• IP addresses, associated with recent attacks, are blocked via the eSentire Global Deny List

What you should do about it

• If not required for a business function, block password-protected zip archives at the email boundary 
• Train employees and other legitimate users of your IT systems to identify and report potentially malicious content 
• Ensure endpoint detection and response technology is deployed across all endpoints
• The eSentire TRU released a previous advisory on Qakbot HTML smuggling here

Additional information

Qakbot malware has been in active use since at least 2007 [1]. Initially, the malware was used to steal victim data, but in recent years it has functioned primarily for reconnaissance and ransomware delivery.

In recently observed incidents, Qakbot was identified gaining initial access through phishing emails. The users received either a Zip archive containing a Windows Script file (.wsf), a PDF document, or an HTML file where they utilized the HTML smuggling method.  This is a notable change from the February Qakbot campaign, where all observed threats were delivered via malicious OneNote attachments. It is likely that threat actors distributing Qakbot are testing alternative delivery mechanisms, as Microsoft announced new security measures that will be applied to Microsoft 365 to combat OneNote abuse starting in April 2023.

In the first pair of incidents, eSentire MDR for Endpoint was able to block the activity from continuing past the initial file execution. eSentire MDR for Endpoint also blocked the activity as it reached the PowerShell scripting stage, which involved a PowerShell script attempting to reach domains associated with a Qakbot infection.

In later observed incidents, eSentire identified a version of Qakbot that retrieved Cobalt Strike immediately. If not identified and remediated immediately, the malware would load Cobalt Strike into the machine's registry and perform basic reconnaissance, though eSentire MDR for Endpoint was able to block any connections attempted. The Cobalt Strike framework is a common ransomware precursor threat.

In all recent incidents, eSentire's proactive threat intelligence feeds and global block lists detected activity on the hosts, which were isolated, alerted, and escalated to the customers for remediation. Due to rapid remediation, secondary payloads and attacker objectives have not been identified.

Indicators of Compromise (IoCs):

References:

[1] https://attack.mitre.org/software/S0650/
[2] https://www.esentire.com/security-advisories/new-qakbot-campaign-observed
[3] https://www.microsoft.com/en-us/security/blog/2021/11/11/html-smuggling-surges-highly-evasive-loader-technique-increasingly-used-in-banking-malware-targeted-attacks/
[4] https://www.esentire.com/security-advisories/ongoing-qakbot-onenote-campaign
[5] OneNote blocks embedded files that have dangerous extensions - Deploy Office | Microsoft Learn