Checks if the trojan is running from the <system folder>. If it isn't running from the system folder, Backdoor:Win32/Simda.A copies itself as <system folder>\<random_number>.exe
Modifies the following registry entry to execute its copy at Windows start:
In subkey: HKLM\Software\Microsoft\Windows NT\Currentversion\Winlogon Sets value: "userinit" With data: "<system folder>\userinit.exe, <system folder>\<random_number>.exe"
Injects code to the process “svchost.exe”
Deletes the original executable
Downloads and executes arbitrary files
Backdoor:Win32/Simda.A connects to a remote host and provides information regarding the newly infected computer.
It then receives the configuration information on where to download additional files, and other locations from which to download additional configuration files. Downloaded files are written to the %TEMP% folder, for example C:\Users\<user name>\AppData\Local\Temp. These files may include additional malware.
In the wild, we have observed the following domains being contacted for this purpose:
Modifies security settings
Backdoor:Win32/Simda.A uses various techniques in an attempt to elevate its privilege. It attempts to log on as Administrator (if the user isn't Admin already) using a list of passwords:
If successful at privilege escalation, Simda attempts to inject a DLL into the process space of winlogon.exe. This DLL is detected as PWS:Win32/Simda.
Backdoor:Win32/Simda.A also attempts to exploit the following vulnerabilities in order to assist in gaining elevated privileges: