Downloader Trojan that can drop multiple malware (Jan 30th, 2015)

The Dell Sonicwall Threats Research team have discovered a downloader Trojan spreading through email. It can drop various kinds of malware on the system. In this case it dropped ransomware that remained dormant on the system.

Infection Cycle:

The Trojan uses the following PDF icon:

The Trojan makes the following DNS queries:

• stun4.l.google.com

The Trojan adds the following files to the filesystem:

• %TEMP%document.exe [Detected as GAV: Upatre.AF_8 (Trojan)]
• %WINDOWS%VTlrgieTqjTrJGf.exe [Detected as GAV: Ransomer.DYG (Trojan)]

The Trojan reports infection to a C&C server using the User Agent “Mazilla/5.0”:

The Trojan downloads an additional malware executable (kora_k12.pdf) from a remote webserver:

The file is encrypted. During analysis we were able to determine the location of the decryption routine in the executable:

After decyption, the file VTlrgieTqjTrJGf.exe is written to disk. The file appears to be a ransomware Trojan but remains dormant on the filesystem. It uses the following icon:

SonicWALL Gateway AntiVirus provides protection against this threat via the following signatures:

• GAV: Upatre.AF_8 (Trojan)
• GAV: Malagent.H_2691 (Trojan)
• GAV: Ransomer.DYG (Trojan)

Security News

The SonicWall Capture Labs Threat Research Team gathers, analyzes and vets cross-vector threat information from the SonicWall Capture Threat network, consisting of global devices and resources, including more than 1 million security sensors in nearly 200 countries and territories. The research team identifies, analyzes, and mitigates critical vulnerabilities and malware daily through in-depth research, which drives protection for all SonicWall customers. In addition to safeguarding networks globally, the research team supports the larger threat intelligence community by releasing weekly deep technical analyses of the most critical threats to small businesses, providing critical knowledge that defenders need to protect their networks.