Virus Name: Joshi
Aliases: Happy Birthday Joshi, Stealth Virus
V Status: Common
Discovered: June, 1990
Symptoms: BSC; machine hangs and message
Eff Length: N/A
Type Code: BRX - Resident Boot Sector/Master Boot Sector Infector
Detection Method: ViruScan, NAV, F-Prot, Sweep, AVTK, IBMAV,
NAVDX, VAlert, PCScan, ChAV
Removal Instructions: NAV, or M-Disk/P
The Joshi virus was isolated in India in June 1990. At the time it
was isolated, it was reported to be widespread in India as well as
portions of the continent of Africa. Joshi is a memory resident
boot sector infector of diskettes and the hard disk master boot
sector (partition table).
After a system has been booted from a Joshi-infected diskette, the
virus will be resident in memory. Joshi takes up approximately 6K
of system memory, and infected systems will show that total system
memory is 6K less than is installed if the DOS CHKDSK program is
Joshi has some similarities to two other boot sector infectors.
Like the Stoned virus, it infects the master boot sector of hard
disks. Similar to the Brain virus's method of redirecting all
attempts to read the boot sector to the original boot sector, Joshi
does this with the master boot sector.
On January 5th of any year, the Joshi virus activates. At that
time, the virus will hang the system while displaying the message:
"type Happy Birthday Joshi"
If the system user then types "Happy Birthday Joshi", the system
will again be usable.
This virus may be recognized on infected systems by powering off
the system and then booting from a known-clean, write-protected DOS
diskette. Using a sector editor or viewer to look at the boot
sector of suspect diskettes, if the first two bytes of the boot
sector are hex EB 1F, then the disk is infected. The EB 1F is a
jump instruction to the rest of the viral code. The remainder of
the virus is stored on track 40, sectors 1 through 5 on 360K 5.25
inch Diskettes. For 1.2M 5.25 inch diskettes, the viral code is
located at track 80, sectors 1 through 5. It will also be located
on the last track of 3.5" diskettes.
To determine if a system's hard disk is infected, you must look at
the hard disk's master boot sector. If the first two bytes of the
master boot sector are EB 1F hex, then the hard disk is infected.
The remainder of the virus can be found at cylinder 0, side 0,
sectors 2 through 6. The original master boot sector will be located
at cylinder 0, side 0, sector 9.
The Joshi virus can be manually removed from an infected system by
first powering off the system, and then booting from a known-clean,
write-protected master DOS diskette. If the system has a hard
disk, the hard disk should have data and program files backed up,
and the original master boot sector copied back to cylinder 0, side
0, sector 1 from sector 9. Diskettes are easier to remove Joshi
from, the DOS SYS command can be used. There are also several
disinfector programs available.
Systems infected with Joshi may experience problems when attempting
to access programs or data files on write protected diskettes.
Known variant(s) of Joshi are:
Joshi-B: Similar to behavior to the original Joshi virus, the
major change with this variant is that when the system
is booted on January 5, the boot will hang with no message
displayed. If the user types "Happy Birthday Joshi", then
the system boot will proceed.
Origin: Unknown May, 1992.