Stoned.Michelangelo

SUMMARY

Stoned.Michelangelo is a virus that infects the DOS boot sector on floppy disks and the master boot record (MBR) of the first hard drive (80h).

Threat Assessment

Wild

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

Damage

• Damage Level: Low

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

The virus copies the original MBR to side 0, cylinder 0, sector 7 on hard drives, logical sector 11 on 360K floppy disks, and logical sector 28 on 1.2 MB floppy disks. Stoned.Michelangelo does not appear to infect 3½-inch floppy disks.

In addition to standard viral replication, Stoned.Michelangelo carries two destructive payloads. The first occurs on floppy disks. If the infected floppy disk contains many directory entries, damage may occur to the last entries in the root directory. This damage appears as a strange filename beginning with three high-bit (high ASCII) characters, followed by the words "MSDOS" or "IBM." These characters are the first part of the floppy disk’s original boot record, which was copied by the virus to a sector near the end of the root directory table. The virus does not check to see if data pre-exists in the target location and, as a result, any data in the target location is overwritten and lost.

The second destructive payload is intentional data destruction on the hard drive. Stoned.Michelangelo triggers on March 6th of every year. If the infected computer is booted at any time on March 6th, the virus silently overwrites the first 17 sectors of the first 256 cylinders of the hard drive with random information from memory. No message or warning is given, although the hard drive light remains on and the system appears to lock up. If the system is immediately turned off, some data may be recoverable. Otherwise, all overwritten areas of the drive are erased beyond recovery by any utility.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.