W32.Welchia.C.Worm

W32.Welchia.C.Worm is a minor variation of, and functionally equivalent to W32.Welchia.B.Worm.

If the version of the operating system of the infected machine is Chinese, Korean, or English, the worm will attempt to download the Microsoft Workstation Service Buffer Overrun and Microsoft Messenger Service Buffer Overrun patches from the Microsoft® Windows Update Web site, install it, and then restart the computer.

The worm also attempts to remove W32.Mydoom.A@mm and W32.Mydoom.B@mm worms.

W32.Welchia.C.Worm exploits multiple vulnerabilities, including:

• The DCOM RPC vulnerability (first described in Microsoft Security Bulletin MS03-026) using TCP port 135. The worm specifically targets Windows XP machines using this exploit. Users are recommended to patch this vulnerability by applying Microsoft Security Bulletin MS03-039.
• The WebDav vulnerability (described in Microsoft Security Bulletin MS03-007) using TCP port 80. The worm specifically targets machines running Microsoft IIS 5.0 using this exploit. The worm's use of this exploit will impact Windows 2000 systems and may impact Windows NT/XP systems.
• The Workstation service buffer overrun vulnerability (described in Microsoft Security Bulletin MS03-049) using TCP port 445. Windows XP users are protected against this vulnerability if Microsoft Security Bulletin MS03-043 has been applied. Windows 2000 users must apply MS03-049.
• The Locator service vulnerability using TCP port 445 (described in Microsoft Security Bulletin MS03-001). The worm specifically targets Windows 2000 machines using this exploit.

The presence of the file, %Windir%\system32\drivers\svchost.exe, is an indication of a possible infection.

This threat is compressed with UPX.

Protection

• Initial Rapid Release version February 17, 2004
• Latest Rapid Release version February 17, 2004
• Initial Daily Certified version February 17, 2004
• Latest Daily Certified version February 17, 2004
• Initial Weekly Certified release date February 18, 2004

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Low

Distribution

• Distribution Level: Medium