Scroll Virus

Virus Name: Scroll Aliases: Scroll.795 V Status: Rare Discovered: October, 1992 Symptoms: .COM file growth; file time seconds set to "62"; decrease in total system & available free memory; file allocation error; .BAT files overwritten Origin: England Eff Length: 795 - 1,306 Bytes Type Code: PRhCK - Parasitic Resident .COM Infector Detection Method: ViruScan, AVTK, F-Prot, Sweep, IBMAV, NAVDX, NAV, VAlert, PCScan, ChAV, NShld, LProt, Sweep/N, Innoc, AVTK/N, NAV/N, IBMAV/N, NProt Removal Instructions: Delete infected files General Comments: The Scroll virus was received from Manchester, England in October, 1992. Scroll is a memory resident infector of .COM programs, including COMMAND.COM. It employs some stealth techniques to avoid the user noticing the file infections. The first time a program infected by the Scroll virus is executed, the Scroll virus will install itself memory resident at the top of system memory but below the 640K DOS boundary. Total system and available free memory, as indicated by the DOS CHKDSK program, will have decreased by 3,008 bytes. Interrupt 21 will be hooked by Scroll in memory. Once memory resident, the Scroll virus will infect .COM programs, including COMMAND.COM, when they are executed or opened for any reason. Infected programs will have a file length increase of 795 to 1,306 bytes which the virus will hide when it is memory resident. The Scroll virus will be located at the end of infected programs. The seconds field in the file's date and time in the DOS disk directory will have been set to "62", the infection marker for the virus. The following text strings are encrypted within the viral code: "[SCROLL] ICE-9 ARcV" "\COMMAND.COM Systems infected with the Scroll virus may notice that the DOS CHKDSK program will detect file allocation errors when the Scroll virus is memory resident. It will also occassionally overwrite .BAT files, permanently corrupting them. Known variant(s) of Scroll are: Scroll.600: Received in January, 1996, this is a 600 byte non-resident variant of Scroll. It infects all of the .COM files in the current directory, except very small ones and COMMAND.COM, when an infected program is executed. Infected programs will have a file length increase of 600 bytes with the virus being located at the end of the file. The program's date and time in the DOS disk directory listing will not appear to be altered, though the seconds field will have been changed to "52". The following text strings are visible within the viral code: ".. *.* *.COM" "Scroll v1.0" Origin: Unknown January, 1996.