| Alias: | D3 |
| Strain: | - |
| detected when: | |
| where: | |
| Classification: | Master-boot record (HD) infector, DBR (Floppy)- infector, re |
| Length: | 1 kilobyte(s) |
Preconditions | |
| Operating System(s): | MS-DOS |
| Version/Release: | All models { MS-DOS/PC-DOS } |
| Computer model(s): | PC's |
| Caroname: | AntiEXE |
Attributes | |
| Easy identification: | |
Type of Infection: | The virus overwrites a constant data area of the file. Bootsector infection. Selfrec in memory: { Doesn't need any - MBR/FBR infector } Selfrec on disk: PDisk[0/0/1][0-3] == Virus[0-3]{ Compares first 4 bytes of MBR/FBR to the virus body } |
| Infection Technique: | |
| Infection Trigger: | Floppies: INT 13/AH=02,CX=00001,DH=0 && DL<=1{ I.e. it attempts to infect a floppy ineither A: or B: drive when the floppy'sBoot record is being read }Hard disk: Boot from an infected floppy { As Stoned } |
| Storage Media affected: | Harddisks, Disketts |
| Interrupts hooked: | 13/AH=02, 13/AH=F9, D3 |
| Stealth: | |
| Tunneling/Selfprot: | |
| Oligo/Polymorphism: | - |
| Encoding Method: | |
| Damage: | Transient: When the virus is active in memory, some (one?) EXEprogram(s) are copied/loaded with a very first bytechanged (i.e. 'MZ' sign is corrupted). Thus, sucha program would be treated by DOS as a COM program,most likely hanging a PC when executed. Permanent: - |
| Damage Trigger: | Transient: First eight bytes of a sector being read are asfollows:DB 'M', 'Z', 40H, 00H, 88H, 01H, 37H, 0FHI.e. the virus hunts for a certain EXE header. Permanent: - |
| Particularities: | The virus resides at the top of memory, reducing the BIOS memory size at 0000:0413. The virus uses a special coding style to fool most disassemblers. As in the case of Stoned, if a floppy being infectedcontains many files/subdirectories in its rootdirectory, several (up to 16) last entriesin the root directory get corrupted. Not displayed text: 'MZ' The virus hunts for a certain unknown EXE program.Besides INT 13/AH=02 (Read Sector(s)) BIOS function,the virus also intercepts INT 13/AH=F9, which is unknownto me. In the case of AH=F9 the virus simply returnsto the caller. |
| Similarities: | |
Agents | |
| Countermeasures: | |
| Standard means: | |
Acknowledgements | |
| Location: | Virus Test Center, University Hamburg, FRG |
| Classification by: | Dmitry O. Gryaznov |
| Documentation by: | Dmitry O. Gryaznov |
| Date: | 1993-09-21 |
| Information Source: | Caroentry (autom.converter by S.Freitag) |
(c) 1996 Virus-Test-Center, University of Hamburg