During the course of ongoing investigations, the FBI identified noticeable increases in computer exploitation attempts against these entities. The specific intrusion vector used against the firms is a spear phishing or targeted socially engineered e-mail designed to compromise a network by bypassing technological network defenses and exploiting the person at the keyboard. Hackers exploit the ability of end users to launch the malicious payloads from within the network by attaching a file to the message or including a link to the domain housing the file and enticing users to click the attachment or link.
Network defense against these attacks is difficult as the subject lines are spoofed, or crafted, in such a way to uniquely engage recipients with content appropriate to their specific business interests. In addition to appearing to originate from a trusted source based on the relevance of the subject line, the attachment name and message body are also crafted to associate with the same specific business interests. Opening a message will not directly compromise the system or network because the malicious payload lies in the attachment or linked domain. Infection occurs once someone opens the attachment or clicks the link, which launches a self-executing file and, through a variety of malicious processes, attempts to download another file.
Indicators are unreliable to flag in-bound messages; however, indicators are available to determine an existing compromise. Once executed, the malicious payload will attempt to download and execute the file ‘srhost.exe’ from the domain ‘http://d.ueopen.com’; e.g. http://d.ueopen.com/srhost.exe. Any traffic associated with ‘ueopen.com’ should be considered as an indication of an existing network compromise and addressed appropriately.
The malicious file does not necessarily appear as an ‘exe’ file in each incident. On occasion, the self-executing file has appeared as other file types, e.g., ‘.zip’, ‘.jpeg’, etc.
Please contact your local field office if you experience this network activity and direct incident response notifications to DHS and U.S. CERT.