| Alias: | |
| Strain: | - |
| detected when: | |
| where: | |
| Classification: | COM and EXE infector, Oerlay infector, Other!??? , resident |
| Length: | 3648 (228 paragraph(s)) |
Preconditions | |
| Operating System(s): | MS-DOS |
| Version/Release: | MS-DOS/PC-DOS >= 2.0 (File handle oriented I/O) |
| Computer model(s): | PC's |
| Caroname: | Warlock |
Attributes | |
| Easy identification: | |
Type of Infection: | The virus appends itself to the files Selfrec in memory: INT_21;AX=D000 -> STC (C-flag set), COMPARES.Additional check is made by a resident virus - itcompares a piece of its code to that of the caller.In the case 21/D000 is spoofed, the virus does notset C-flag Selfrec on disk: File[EOF-4] == 0B0Dh (0Dh, 0Bh) |
| Infection Technique: | |
| Infection Trigger: | (Exec or(Open or Rename or ChMod) andFileExt in [.EXE, .COM, .OVL, .DBF]) and(FileName != "COMMAND.COM") and(LengthCOM > 1024) and (LengthCOM < 62687) and(LengthEXE <= EXE_Image_Size (i.e. EXE file isnot segmented)) and (EXE_IP != 0eh (all LZEXE-packedfiles, in particular AIDSTEST scanner)) and(EXE_stack < EXE_Image_Size orEXE_stack > EXE_Image_Size+72h (a bug - should be 720h)) |
| Storage Media affected: | |
| Interrupts hooked: | 21/4B, 21/3D, 21/43, 21/56, 21/D000, 24, 2A |
| Stealth: | |
| Tunneling/Selfprot: | |
| Oligo/Polymorphism: | - |
| Encoding Method: | |
| Damage: | Transient: Permanent: First 32 bytes of DBF files are overwritten with 0C3Hvalue. |
| Damage Trigger: | Transient: Permanent: File[0]==03 (usually .DBF files signature) and(Exec or Open or Rename or Get/Set File Attr.) |
| Particularities: | The virus resides above the last MCB Overlays damaged, some EXE files won't operateproperly - the virus body might be overwritten byprogram's stack. Not displayed text: "Revenge of WARLOCK!"; Encrypted"STACK STACK STACK STAC"; Encrypted"COMMAND.COM"; Encrypted"EXE"; Encrypted"OVL"; Encrypted"DBF"; Encrypted Tunnelling is borrowed from Yankee_Doodle.TP.For some MS-DOS versions (prev. to 4.0 - namely, ifthe DOS int 21 handler starts with CMP AH,[TopFunc])the virus patches direct DOS entry with JMP FAR V_SEG:V_OFS.Otherwise, it simply intercepts int 21 vector. |
| Similarities: | |
Agents | |
| Countermeasures: | |
| Standard means: | |
Acknowledgements | |
| Location: | Virus Test Center, University Hamburg, FRG |
| Classification by: | Dmitry O. Gryaznov |
| Documentation by: | Dmitry O. Gryaznov |
| Date: | 1993-07-17 |
| Information Source: | Caroentry (autom.converter by S.Freitag) |
(c) 1996 Virus-Test-Center, University of Hamburg