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Cybercriminals Exploit Google Cloud Run in Extensive Banking Trojan Scheme

 

Security experts have issued a warning about hackers exploiting Google Cloud Run to distribute significant amounts of banking trojans such as Astaroth, Mekotio, and Ousaban.

Google Cloud Run enables users to deploy various services, websites, or applications without the need to manage infrastructure or worry about scaling efforts.

Starting from September 2023, researchers from Cisco Talos observed a notable surge in the misuse of Google's service for spreading malware. Brazilian actors initiated campaigns utilizing MSI installer files to distribute malware payloads. According to the researchers' findings, cybercriminals are increasingly drawn to Google Cloud Run due to its cost efficiency and its ability to circumvent conventional security measures.

The attack methodology typically begins with phishing emails sent to potential victims, disguised to resemble authentic communications such as invoices, financial statements, or messages from local government and tax authorities. While most emails in these campaigns are in Spanish to target Latin American countries, some also use Italian. These emails contain links that redirect to malicious web services hosted on Google Cloud Run.

In certain instances, the malware payload is delivered through MSI files, while in others, the service redirects to a Google Cloud Storage location, housing a ZIP archive containing a malicious MSI file. Upon execution of these malicious files, additional components and payloads are downloaded and executed on the victim's system.

Furthermore, the malware establishes persistence on the victim's system to survive reboots by creating LNK files in the Startup folder, configured to execute a PowerShell command that triggers the infection script.

The campaigns exploiting Google Cloud Run involve three primary banking trojans: Astaroth/Guildma, Mekotio, and Ousaban. Each of these trojans is designed to infiltrate systems covertly, establish persistence, and extract sensitive financial data, which can be utilized for unauthorized access to banking accounts.

Astaroth employs advanced evasion techniques and has expanded its targets beyond Brazil to encompass over 300 financial institutions across 15 Latin American countries. It has recently begun targeting credentials for cryptocurrency exchange services.

Similarly, Mekotio, active for several years, focuses on the Latin American region, specializing in stealing banking credentials, personal information, and executing fraudulent transactions.

Ousaban, another banking trojan, conducts keylogging, captures screenshots, and engages in phishing for banking credentials using counterfeit banking portals. Cisco Talos suggests a potential collaboration between the operators of Astaroth and Ousaban due to the latter being delivered in the later stages of the former's infection chain.

In response to these findings, Google has taken action by removing the malicious links and is exploring ways to enhance its mitigation efforts to combat such malicious activities.

This New Phishing Attack Uses a Weaponized Excel File

 

A new phishing campaign is targeting financial sector employees by using links to download a ‘weaponized’ Excel document.

MirrorBlast, a phishing effort, was discovered in early September by security firm ET Labs. Morphisec, a fellow security firm, has now studied the malware and warns that the malicious Excel files might escape malware-detection systems due to "extremely lightweight" embedded macros, making it especially risky for businesses that rely on detection-based protection and sandboxing. 

Macros, or scripts for automating activities, have grown in popularity among cybercriminals. Despite the fact that macros are disabled by default in Excel, attackers employ social engineering to deceive potential victims into allowing macros. Despite appearing to be a simple approach, macros have been employed by state-sponsored hackers because they frequently work. 

Microsoft earlier this year extended its Antimalware Scan Interface (AMSI) for antivirus to combat the rise in macro malware and a recent phenomenon by attackers to utilise outdated Excel 4.0 XLM macros (rather than newer VBA macros) to circumvent anti-malware systems. 

As per Morphisec, the MirrorBlast attack chain is similar to tactics used by TA505, a well-established, financially focused Russia-based cybercriminal group. The group has been active since at least 2014 and is well-known for its usage of a wide range of tools. 

Morphisec researcher Arnold Osipov stated in a blog post, "TA505 is most known for frequently changing the malware they use as well as driving global trends in malware distribution." 

While the MirrorBlast attack begins with a document attached to an email, it afterwards uses a Google feed proxy URL with a SharePoint and OneDrive trap that masquerades as a file-sharing request. When the user clicks the URL, they are sent to a hacked SharePoint site or a bogus OneDrive site. Both versions will take to the malicious Excel document. 

The sample MirrorBlast email demonstrates how the attackers are capitalising on company-issued data on COVID-related modifications to working conditions. Morphisec points out that due to compatibility issues with ActiveX components, the macro code can only be run on a 32-bit version of Office. The macro itself runs a JavaScript script meant to avoid sandboxing by determining if the computer is in administrator mode. The msiexec.exe process is then launched, which downloads and instals an MSI package. 

Morphisec discovered two MIS installation versions that employed legal scripting tools named KiXtart and REBOL. The KiXtart script transmits information about the victim's workstation to the attacker's command and control server, including the domain, computer name, user name, and process list. It then answers with a number indicating whether the Rebol version should be used. Morphisec states that the Rebol script leads to a remote access tool called FlawedGrace, which the group has previously utilised. 

Osipov added, "TA505 is one of many financially motivated threat groups currently active in the marketplace. They are also one of the most creative, as they have a tendency to constantly shift the attacks they leverage to achieve their goals."