Yap Virus

 Virus Name:  Yap 
 V Status:    Rare 
 Discovered:  March, 1991 
 Symptoms:    .COM growth; TSR; "Bugs" may appear in screen; decrease in 
              available free memory 
 Origin:      United States 
 Eff Length:  6,258 Bytes 
 Type Code:   PRsCK - Parasitic Resident .COM Infector 
 Detection Method:  ViruScan, AVTK, NAV, F-Prot, Sweep, IBMAV, ChAV, 
                    NAVDX, VAlert, PCScan, 
                    NShld, LProt, Sweep/N, Innoc, NProt, AVTK/N, NAV/N, 
 Removal Instructions:  Delete infected files 
 General Comments: 
       The Yap virus was discovered in March, 1991, in the United States. 
       Yap is a memory resident .COM file infector.  It will infect 
       The first time a program infected with the Yap virus is executed, 
       the virus will install itself memory resident as a low system 
       memory TSR of 11,344 bytes.  Interrupts 09 and 21 will be hooked by 
       the virus. 
       After Yap is memory resident, it will infect .COM programs as they 
       are executed.  If COMMAND.COM is executed, it will become infected. 
       .COM Programs infected with Yap will increase in size by 6,258 
       bytes. The virus will be located at the end of infected programs. 
       The file's date and time in the disk directory will not be altered. 
       With the Yap virus memory resident, if the system user holds down 
       the ALT key, or presses the ALT key and another key in combination, 
       numerous graphic "bugs" will appear on the screen which will eat 
       the contents of the system display.  Pressing the ALT key, or ALT 
       key combination, again will result in the system's display being 
       Yap is an encrypted virus, using encryption very similar to that 
       employed by the Cascade virus and its variants. 

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