Tinba 2 (DGA) banking trojan

Hunt Hypothesis

This hunt hypothesis targets adversaries deploying the Tinba banking Trojan to establish persistence and exfiltrate credentials via Domain Generation Algorithm (DGA) communication patterns that may evade standard signature-based detection. Proactively hunting for these specific DGA behaviors in Azure Sentinel is critical because early identification of this low-severity activity can prevent lateral movement and financial data theft before the malware escalates its impact on the banking infrastructure.

YARA Rule

rule Tinba2 : banking {
        meta:
                author = "n3sfox <[email protected]>"
                date = "2015/11/07"
                description = "Tinba 2 (DGA) banking trojan"
                reference = "https://securityintelligence.com/tinba-malware-reloaded-and-attacking-banks-around-the-world"
                filetype = "memory"
                hash1 = "c7f662594f07776ab047b322150f6ed0"
                hash2 = "dc71ef1e55f1ddb36b3c41b1b95ae586"
                hash3 = "b788155cb82a7600f2ed1965cffc1e88"

        strings:
                $str1 = "MapViewOfFile"
                $str2 = "OpenFileMapping"
                $str3 = "NtCreateUserProcess"
                $str4 = "NtQueryDirectoryFile"
                $str5 = "RtlCreateUserThread"
                $str6 = "DeleteUrlCacheEntry"
                $str7 = "PR_Read"
                $str8 = "PR_Write"
                $pubkey = "BEGIN PUBLIC KEY"
                $code1 = {50 87 44 24 04 6A ?? E8}

        condition:
                all of ($str*) and $pubkey and $code1
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 10 string patterns in its detection logic.

References

• https://securityintelligence.com/tinba-malware-reloaded-and-attacking-banks-around-the-world
• Source Rule

False Positive Guidance

Here are specific false positive scenarios for the Tinba 2 (DGA) banking trojan detection rule in an enterprise environment:

• Automated Certificate Authority Renewals via PowerShell Scripts

  • Scenario: Scheduled administrative tasks using PowerShell or certutil.exe to renew SSL certificates often generate DNS queries for random subdomains of certificate authorities (e.g., random-string.digicert.com, unique-id.verisign.com). These high-entropy domain names mimic the Domain Generation Algorithm (DGA) patterns typical of Tinba.
  • Filter/Exclusion: Exclude traffic where the source process name is powershell.exe or certutil.exe and the destination domain matches known Certificate Authority TLDs (e.g., *.digicert.com, *.verisign.com, *.letsencrypt.org).

• Software Update Manifest Fetching by Antivirus Engines

  • Scenario: Endpoint protection tools like CrowdStrike Falcon, Microsoft Defender for Endpoint, or Symantec Endpoint Protection frequently query dynamic update servers to download definition manifests. These queries often utilize hash-based subdomains (e.g., a1b2c3d4-update.microsoft.com) that resemble DGA traffic, especially during off-hours when bulk updates occur.
  • Filter/Exclusion: Create an allowlist for the specific executable paths of major EDR agents (e.g., C:\Program Files\Microsoft Defender\MsMpEng.exe, C:\ProgramData\CrowdStrike\fsa.exe) communicating with known vendor update domains.

• Cloud Storage Synchronization and Block-Level Deduplication

  • Scenario: Enterprise file synchronization tools like OneDrive for Business, Dropbox Business, or Box generate unique, high-entropy domain names when establishing connections to specific storage nodes or