HiDos Virus

 Virus Name:  HiDos 
 V Status:    Rare 
 Discovered:  November, 1992 
 Symptoms:    BSC; master boot sector altered; decrease in total system & 
              available free memory; system hangs; diskette root directory 
 Origin:      England 
 Eff Length:  N/A 
 Type Code:   BRtX - Resident Boot Sector & Master Boot Sector Infector 
 Detection Method:  ViruScan, F-Prot, AVTK, IBMAV, NAV, 
                    Sweep, NAVDX, Valert, PCScan, ChAV 
 Removal Instructions:  Delete infected files 
 General Comments: 
       The HiDos boot virus was submitted in November, 1992.  It is from 
       England.  HiDos is a memory resident infector of diskette boot 
       sectors and the system hard disk master boot sector (partition 
       table).  It is roughly based on the Stoned virus. 
       The first time the system is booted from a diskette infected with 
       the HiDos virus, the HiDos virus will infect the system hard disk 
       master boot sector and become memory resident.  Total system and 
       available free memory, as indicated by the DOS CHKDSK program, will 
       have decreased by 2,048 bytes.  On the system hard disk, the original 
       master boot sector will have been moved to Side 0, Cylinder 0, Sector 
       7, and a copy of the viral code written to the original master boot 
       sector location. 
       Once the HiDos Boot virus is memory resident, it will occassionally 
       infect the boot sector of non-write protected diskettes which are 
       accessed on the system.  The infection always occurs when the user 
       changes current drives from the system hard disk to the diskette 
       drive, with a system hang resulting.  Any attempt to directly access 
       the diskette boot sector or the system hard disk's master boot 
       sector will also result in a system hang. 
       The original boot sector of infected 360K 5.25" diskettes will have 
       been copied to sector 11.  On 1.2M 5.25" diskettes, it will be at 
       sector 17.  As both of these sectors are part of the root directory, 
       directory corruption may result if they previously contained entries. 

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