Cisco Security Intelligence Operations has detected significant activity related to spam e-mail messages that appear to contain a PDF document in an attachment for the recipient. The e-mail message does not contain any message body or subject line. However, the .zip attachment contains a malicious .exe file that, when executed, attempts to infect the system with malicious code.
E-mail messages that are related to this threat (RuleID3331) may contain the following files:
The EX-38463.pdf.exe file has a file size of 14,848 bytes. The MD5 checksum, which is a unique identifier of the executable, is the following string: 0x5085794E6C283EBCFA3878805B9E7BE7
The malware associated with this threat outbreak is determined by multiple security vendors as belonging to the Chepvil class of backdoor trojans. This trojan could modify the system registry and could download and install additional malware on the system by communicating with arbitrary hosts on the Internet.
Cisco Security Intelligence Operations analysts examine real-world e-mail traffic data that is collected from over 100,000 contributing organizations worldwide. This data helps provide a range of information about and analysis of global e-mail security threats and trends. Cisco will continue to monitor this threat and automatically adapt IronPort systems to protect customers. This report will be updated if there are significant changes or if the risk to end users increases.
Cisco IronPort Virus Outbreak Filters protect customers during the critical period between the first exploit of a virus outbreak and the release of vendor antivirus signatures. E-mail that is managed by Cisco and end users who are protected by Cisco IronPort web security appliances will not be impacted by these attacks. Cisco IronPort appliances are automatically updated to prevent both spam e-mail and hostile web URLs from being passed to the end user.
Cisco Security Intelligence Operations
Cisco Threat Operations Center
Cisco SenderBase Security Network