Azusa Virus

 Virus Name:  Azusa 
 Aliases:     Hong Kong 
 V Status:    Common 
 Discovery:   February, 1991 
 Symptoms:    BSR; decrease in total system and available free memory; 
              LPT1 & COM1 ports may be disabled 
 Origin:      Hong Kong 
 Eff Length:  N/A 
 Type Code:   BRtX - Resident Boot Sector & Master Boot Sector Infector 
 Detection Method:  ViruScan, F-Prot, NAV, Sweep, AVTK, IBMAV, 
                    NAVDX, VAlert, PCScan, ChAV 
 Removal Instructions:  M-Disk/P, FDisk /MBR on DOS 5 systems 
 General Comments: 
       The Azusa virus was received in February, 1991.  Its origin is 
       unknown, though its origin is believed to be Hong Kong.  This virus 
       is a memory resident infector of diskette boot sectors and the hard 
       disk master boot sector (partition table). 
       The first time the system is booted from a diskette infected with 
       the Azusa virus, the virus will become memory resident at the top of 
       system memory, but below the 640K DOS boundary.  The virus moves the 
       Interrupt 12 return so that the system will report 1,024 bytes less 
       memory than is installed on the system.  At this time, the virus 
       will infect the system's hard disk master boot sector, overwriting 
       the master boot sector with a copy of the Azusa virus.  A copy of 
       the original master boot sector is not stored by the virus. 
       Once Azusa is memory resident, it will infect diskettes when they 
       are accessed on the system with write intent (i.e., a file is opened 
       as output, or with read/write intent) or when attempting to reboot 
       the system from a diskette via CTL-ALT-DEL.  Diskettes are infected 
       by copying the original diskette boot sector to track 40 sector 8, 
       and then writing a copy of itself to the diskette's boot sector.  On 
       diskettes other than 360K 5.25" diskettes, the original boot sector 
       will end up in the middle of the disk, possibly corrupting files. 
       The Azusa virus keeps track of how many times the system has been 
       booted from an infected diskette.  After 32 boots, the virus will 
       disable the COM1 and LPT1 ports on the system, and reset its 
       counter. A later boot will result in the ports functioning properly 
       Known variant(s) of Azusa are: 
       Azusa 2: Submitted in April, 1991, this variant is from Hong Kong. 
                The memory resident portion of Azusa 2 is 2,048 bytes in 
                length, located at the top of system memory but below the 
                640K DOS boundary.  Infection of high-density diskettes 
                will result in severe cross-linking of files and invalid 
                clusters, as well as 0 bytes in directories.  CTRL-C may 
                fail to function, as well as boots from infected diskettes 
                may hang the system.  Disabling of COM1 and LPT1 may also 
                be experienced. 
       See:   Evil Empire 

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