There is yet another reason to be wary of spam email about bank transfers or invoices -- it could be carrying a new, cleverly designed malware program that steals financial information.
Most Trojan programs steal financial information from users by injecting rogue forms into Web browsing sessions, but a newly discovered malware program takes a different approach and leverages browser network APIs to sniff outgoing traffic.
The new threat has been named Emotet by security researchers from antivirus vendor Trend Micro, who recently analyzed variants targeting the customers of several German banks. The malware is distributed via malicious links in spam email messages that masquerade as bank transfer notifications or invoices.
When it first runs on the system, Emotet downloads some additional components and a configuration file that contains the URLs and other strings it will search for inside network traffic.
The configuration files analyzed so far appeared to primarily target German bank websites, but there might be variants targeting banks from other countries, the Trend Micro researchers said in a blog post Friday.
The main Emotet component downloads a DLL file and injects it into all processes running on the system, including Web browsers. The file has the capability to monitor outgoing network traffic from those processes and look for strings specified in the configuration file.
"If strings match, the malware assembles the information by getting the URL accessed and the data sent," the Trend Micro researchers said. "The malware saves the whole content of the website, meaning that any data can be stolen and saved."
The DLL component can also sniff data from encrypted browsing sessions because it hooks directly into the network APIs (application programming interfaces) used by browsers.
This method of stealing information is much harder to detect by users than those involving phishing or rogue form fields injected into pages, the Trend Micro researchers said. "Users can go about with their online banking without ever realizing that information is being stolen."
Another interesting aspect of Emotet is that it encrypts the stolen data and stores it in the system's registry. This is likely another attempt to avoid detection by not creating files on the system.
According to Trend Micro's data, the largest number of Emotet infections were detected in Europe, especially in Germany.
However, Emotet infections have also been detected in other regions, like Asia-Pacific and North America, suggesting that the threat is not exclusive to a specific region or country, the Trend Micro researchers said.