| Alias: | Cascade B-Virus |
| Strain: | Cascade =Autumn =Herbst(laub)-Virus |
| detected when: | |
| where: | |
| Classification: | Program Virus (extending .COM), RAM resident |
| Length: | .COM-file length increases by 1701 byte |
Preconditions | |
| Operating System(s): | MS-DOS |
| Version/Release: | 2.xx upward |
| Computer model(s): | IBM-PC, XT, AT and compatibles |
| Caroname: | Cascade.1701.A |
Attributes | |
| Easy identification: | --- |
Type of Infection: | System: is infected if the call of interrupt 21h with function 4Bh and subfunction FFh is possible and without error and 55AAh is returned in DI- register. .COM file: Program virus: increases COM files by 1701 Byte; a .COM file is infected if the first instruction is a three byte jump with DISP16 = (filelength minus viruslength). .EXE file: no infection. |
| Infection Technique: | |
| Infection Trigger: | Infects all files that are loaded via the function 4Bh and subfunction 00h of the interrupt 21h (MS-DOS uses this function to start any program) |
| Storage Media affected: | |
| Interrupts hooked: | Int21h, Int28h (only if Clockdevice Year = 1980), Int1Ch (only if damage is triggered) |
| Stealth: | |
| Tunneling/Selfprot: | |
| Oligo/Polymorphism: | |
| Encoding Method: | |
| Damage: | Transient Damage: Modifies the screen by making the characters on the screen "fall down" on the screen in connection with clicking noises. |
| Damage Trigger: | IF function GetDate returns with 1. ( year=1988 AND month>=10 ) OR 2. ( year=1980 AND 2.1 clock is changed by user to year=1988, month>=10 OR 2.2 clock is changed by user to year>1988 ) AND a random number generator activates damage. |
| Particularities: | 1. If the system is _not_ infected, the invocation of an infected programm produces errors (system crash is possible). 2. COM-files up to a length of 63803 bytes will be infected, but files with a length of more than 63576 bytes are not loadable after infection. 3. The virus-program is encoded, dependent of the .COM-filelength. 4. The distinction between .EXE and .COM files is made by testing the "magic number (MZ)" in the .EXE-Header. |
| Similarities: | The 1701-Virus is a patch of the Autumn Virus (=1704-Virus), with the following changes: 1) The Filelength will increase by 1701 Bytes. 2) The analysis of the BIOS-Copyright string is not active. 3) COM-Files up to a length of 63803 will be infected. |
Agents | |
| Countermeasures: | ANTI1701.EXE is an antivirus that only looks for the 1701-Virus and, if requested, will restore the file. |
| Standard means: | --- |
Acknowledgements | |
| Location: | Virus Test Center, University Hamburg, FRG |
| Classification by: | Michael Reinschmiedt |
| Documentation by: | Michael Reinschmiedt Morton Swimmer |
| Date: | July 30, 1989 |
| Information Source: | |
(c) 1996 Virus-Test-Center, University of Hamburg