The virus code is one sector in length and it reserves 4K of memory. Thus, on a 640K machine, CHKDSK would report 651,264 bytes of free memory.
On the hard drive, the original MBR is stored on physical sector 7 of the infected drive. The virus stores the original DOS boot sector in the physical sector at side 1, cylinder 0, sector 3 on infected floppy disks (logical sector 11). On 360K floppy disks, this is the last sector of the root directory. It overwrites the last 16 directory entries if the directory is completely full. On larger-capacity floppy disks, it is stored earlier in the root directory.
Upon booting from an infected disk, Stoned.Standard checks the MBR to see if it is infected. If it is not, the virus infects it. This is the only time the hard drive can be infected. If you remove the virus from the MBR while it is active in memory, the MBR is not re-infected. Also, on booting, there is a 1 in 8 chance the virus will beep and display its message.
The infected boot sector or MBR contains the plainly visible message:
Your PC is now stoned! LEGALIZE MARIJUANA!
The message starts at offset 18Ah in the sector. By looking at the floppy boot or MBR sector with a disk editor, you can verify an infection. There is also a fairly common minor variant, which is detected by most anti-virus packages as being the same virus, in which the “LEGALIZE MARIJUANA” portion of the message has been corrupted.
Stoned.Standard was programmed by a University of Wellington student in New Zealand in 1987. By design, the virus infects MBRs and the boot sector of 360K disks. Under such conditions, the virus is relatively benign. However, the virus can damage data on any floppy disk it infects and the probability of damage increases as the capacity of the floppy disk increases. For example, on a 1.44 MB floppy disk, the virus overwrites entries 17-32 in the root.
Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":