CoffeeLoader: A Brew of Stealthy Techniques
Summary:
CoffeeLoader is a sophisticated malware loader identified by security firm Zscaler in September 2024, designed to download and execute second-stage payloads while evading detection by security solutions. It employs a variety of advanced techniques, such as using a specialized packer called Armoury, which executes code on the system's GPU to complicate analysis in virtual environments. CoffeeLoader also incorporates methods like call stack spoofing, sleep obfuscation, and the use of Windows fibers to bypass endpoint security. It is typically distributed via SmokeLoader and can leverage a domain generation algorithm to create backup command-and-control (C2) domains if primary channels are blocked. The malware communicates with its C2 server via HTTPS, using encrypted binary protocols and certificate pinning to prevent man-in-the-middle attacks. Once executed, CoffeeLoader will establish persistence via the creation of scheduled tasks and proceed to inject or run additional malicious payloads, including Rhadamanthys, a notorious information stealer.
Security Officer Comments:
Zscaler has identified several similarities between CoffeeLoader and SmokeLoader, including the use of a stager to inject the main module into another process, the generation of a bot ID based on the computer name and volume serial number, and the creation of a mutex name based on the bot ID. Both malware families resolve imports by hash and encrypt network traffic using hardcoded RC4 keys. They also make extensive use of low-level Windows APIs, set the malware’s file attributes to FILE_ATTRIBUTE_SYSTEM and FILE_ATTRIBUTE_HIDDEN, and utilize scheduled tasks for persistence. While a new version of SmokeLoader was announced in December 2024, it's still unclear whether CoffeeLoader is a new iteration or if these overlaps are coincidental. Nevertheless, CoffeeLoader's ability to evade detection by antivirus software, endpoint detection and response systems, and malware sandboxes makes it a highly appealing tool for adversaries to use in attacks.
Suggested Corrections:
IOCs can be accessed here.
CoffeeLoader is being distributed via Smokeloader which typically relies on social engineer and phishing attacks as a means for propagation. In general, users should:
Be cautious of individuals or organizations that ask for personal information. Most companies will not ask for sensitive data from its customers. If in doubt, users should verify with the company itself to avoid any potential issues.
Take a close look at the sender’s display name when checking the legitimacy of an email. Most companies use a single domain for their URLs and emails, so a message that originates from a different domain is a red flag.
Not click links or download files even if they come from seemingly “trustworthy” sources.
Check for mismatched URLs. While an embedded URL might seem perfectly valid, hovering above it might show a different web address. In fact, users should avoid clicking links in emails unless they are certain that it is a legitimate link.
Be on the lookout for any grammatical errors and spelling mistakes. Legitimate companies will often employ proofreaders and editors who ensure that the materials they send out are error-free.
Not be frightened or intimidated by messages that have an alarmist tone. They should double check with the company if they are uncertain about the status of their accounts.
Phishing emails are designed to be sent to a large number of people, so they need to be as impersonal as possible. Users should check whether the message contains a generic subject and greeting, as this can be a sign of a phishing attempt.
Although not every end user has access to advanced anti-phishing software, they can still use the built-in protection of their email clients to filter messages. One example is setting the email client to block all images unless approved.
Legitimate companies will never send confirmation emails unless there are specific reasons for doing so. In fact, most companies will avoid sending unsolicited messages unless it’s for company updates, newsletters, or advertising purposes.
Users should always take the context of an email or message into account. For example, most online accounts do away with viewable member numbers, so users should be wary if they receive emails containing a “member number” for services that generally don’t use them.
It is important to take note of unusual information in the text of the message. Any mentions of operating systems and software that are not typically used by consumers can often be indicators of a phishing attempt.
If it seems suspicious, it probably is. Users should always err on the side of caution when it comes to sending out personally identifiable information through messages and emails.
Link(s):
https://www.zscaler.com/blogs/security-research/coffeeloader-brew-stealthy-techniques
CoffeeLoader is a sophisticated malware loader identified by security firm Zscaler in September 2024, designed to download and execute second-stage payloads while evading detection by security solutions. It employs a variety of advanced techniques, such as using a specialized packer called Armoury, which executes code on the system's GPU to complicate analysis in virtual environments. CoffeeLoader also incorporates methods like call stack spoofing, sleep obfuscation, and the use of Windows fibers to bypass endpoint security. It is typically distributed via SmokeLoader and can leverage a domain generation algorithm to create backup command-and-control (C2) domains if primary channels are blocked. The malware communicates with its C2 server via HTTPS, using encrypted binary protocols and certificate pinning to prevent man-in-the-middle attacks. Once executed, CoffeeLoader will establish persistence via the creation of scheduled tasks and proceed to inject or run additional malicious payloads, including Rhadamanthys, a notorious information stealer.
Security Officer Comments:
Zscaler has identified several similarities between CoffeeLoader and SmokeLoader, including the use of a stager to inject the main module into another process, the generation of a bot ID based on the computer name and volume serial number, and the creation of a mutex name based on the bot ID. Both malware families resolve imports by hash and encrypt network traffic using hardcoded RC4 keys. They also make extensive use of low-level Windows APIs, set the malware’s file attributes to FILE_ATTRIBUTE_SYSTEM and FILE_ATTRIBUTE_HIDDEN, and utilize scheduled tasks for persistence. While a new version of SmokeLoader was announced in December 2024, it's still unclear whether CoffeeLoader is a new iteration or if these overlaps are coincidental. Nevertheless, CoffeeLoader's ability to evade detection by antivirus software, endpoint detection and response systems, and malware sandboxes makes it a highly appealing tool for adversaries to use in attacks.
Suggested Corrections:
IOCs can be accessed here.
CoffeeLoader is being distributed via Smokeloader which typically relies on social engineer and phishing attacks as a means for propagation. In general, users should:
Be cautious of individuals or organizations that ask for personal information. Most companies will not ask for sensitive data from its customers. If in doubt, users should verify with the company itself to avoid any potential issues.
Take a close look at the sender’s display name when checking the legitimacy of an email. Most companies use a single domain for their URLs and emails, so a message that originates from a different domain is a red flag.
Not click links or download files even if they come from seemingly “trustworthy” sources.
Check for mismatched URLs. While an embedded URL might seem perfectly valid, hovering above it might show a different web address. In fact, users should avoid clicking links in emails unless they are certain that it is a legitimate link.
Be on the lookout for any grammatical errors and spelling mistakes. Legitimate companies will often employ proofreaders and editors who ensure that the materials they send out are error-free.
Not be frightened or intimidated by messages that have an alarmist tone. They should double check with the company if they are uncertain about the status of their accounts.
Phishing emails are designed to be sent to a large number of people, so they need to be as impersonal as possible. Users should check whether the message contains a generic subject and greeting, as this can be a sign of a phishing attempt.
Although not every end user has access to advanced anti-phishing software, they can still use the built-in protection of their email clients to filter messages. One example is setting the email client to block all images unless approved.
Legitimate companies will never send confirmation emails unless there are specific reasons for doing so. In fact, most companies will avoid sending unsolicited messages unless it’s for company updates, newsletters, or advertising purposes.
Users should always take the context of an email or message into account. For example, most online accounts do away with viewable member numbers, so users should be wary if they receive emails containing a “member number” for services that generally don’t use them.
It is important to take note of unusual information in the text of the message. Any mentions of operating systems and software that are not typically used by consumers can often be indicators of a phishing attempt.
If it seems suspicious, it probably is. Users should always err on the side of caution when it comes to sending out personally identifiable information through messages and emails.
Link(s):
https://www.zscaler.com/blogs/security-research/coffeeloader-brew-stealthy-techniques