Sinit

Classification

Malware

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Sinit, Backdoor.Win32.Sinit.f

Summary

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.

Automatic action

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.

Suspect a file is incorrectly detected (a False Positive)?

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note You need administrative rights to change the settings.

For more Support

Knowledge Base

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User Guide

See the user guide for your product on the Help Center.

Contact Support

Chat with or call an expert for help.

Submit a sample

Submit a file or URL for further analysis.

Technical Details

System installation

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"
 

Backdoor

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.