Backdoor:Win32/Xinia.B is a backdoor trojan that allows unauthorized access and control of an affected system. In the wild, this trojan has been distributed in spam, masquerading as a document with a .CHM file extension that discusses the Chinese government's influence on media during the 2008 Beijing Olympic games.
When the .CHM attachment to the spammed e-mail is opened, a document is displayed that references free speech in China.
The trojan's executable is then dropped to c:\windows\downloaded program files\winupdate.exe and executed.
When winupdate.exe executes, it creates the mutex "UTTERRE" to ensure that only one instance runs at any time on the affected system. It then copies itself to <system folder>\tlntsvr.exe and <system folder>\dllcache\tlntsvr.exe.
Backdoor:Win32/Xinia.B also drops a DLL component to <system folder>\lottery.dll. This file is detected as Backdoor:Win32/Xinia.B.dll, and is used to perform the trojan's payload (see below for additional detail). The DLL is injected into the explorer process in order to mask its activity.
Note - <system folder> refers to a variable location that is determined by the malware by querying the Operating System. The default installation location for the System folder for Windows 2000 and NT is C:\Winnt\System32; and for XP and Vista is C:\Windows\System32.
Backdoor Functionality/Steals Sensitive Data
The trojan opens a random TCP port and listens for instructions.
It also records keystrokes for each active window, and collects system information such as OS, system memory, and infection data. The trojan sends the collected information to prideandprejudice.3322.org using port 8000. It may also receive instructions from this remote server.
Analysis by Hong Jia