W32.Lorsis.Worm

W32.Lorsis.Worm is a worm that spreads through the KaZaA file-sharing network. If this worm is executed in February, or from December 6 to 31, it deletes critical system files.

The worm uses several different filenames ending with " .exe" (there are 15 spaces before the .exe extension); see the "Technical Details" section for a complete list.

During execution, the worm repeatedly attempts to copy itself to the A: drive, resulting in noticeable noise from the floppy drive, if one is installed.

W32.Lorsis.Worm is written in Visual Basic and is compressed with Aspack and UPX.

Protection

• Initial Rapid Release version July 28, 2003
• Latest Rapid Release version July 12, 2008 revision 018
• Initial Daily Certified version July 28, 2003
• Latest Daily Certified version July 12, 2008 revision 019
• Initial Weekly Certified release date July 30, 2003

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: High

Distribution

• Distribution Level: Medium