Sinit is a backdoor that opens a random UDP port and allows unauthorized access to infected machine. According to reports, this port can be used as a part of peer-to-peer network enabling uncentralized distribution of malware to infected computers.
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
When run, the backdoor copies itself to the System directory as 'svcinit.exe'. It adds the following registry key to ensure it will be executed when the system is started:
[HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon] "Userinit" = "%System%\userinit.exe,%System%\svcinit.exe"
If the system is running windows 9x (95, 98 or ME), it uses the following key instead:
[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices] "SVC Service" = "%System%\svcinit.exe"
Sinit opens two UDP ports, port 53 and a random port. Using these ports, the backdoor can receive updates and other programs. It should be noted that domain name protocol (DNS) also uses UDP port 53, but the protocol is completely different.
The backdoor also opens a TCP port 53 which acts as a simple HTTP server. When a HTTP GET request for 'ks.exe' or 'kx.htm' is received, the backdoor sends a copy of itself.
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