| Alias: | |
| Strain: | - |
| detected when: | |
| where: | |
| Classification: | COM-infector, resident |
| Length: | NONE |
Preconditions | |
| Operating System(s): | MS-DOS |
| Version/Release: | All models |
| Computer model(s): | PC's |
| Caroname: | Iper |
Attributes | |
| Easy identification: | |
Type of Infection: | The virus appends itself to the files Selfrec in memory: Int_13_vector == 505h Selfrec on disk: File[EOF-7] == "IPER" |
| Infection Technique: | |
| Infection Trigger: | attribute == "normal" && File[0] == 0E9h |
| Storage Media affected: | |
| Interrupts hooked: | 13 |
| Stealth: | |
| Tunneling/Selfprot: | |
| Oligo/Polymorphism: | - |
| Encoding Method: | |
| Damage: | Transient: baudrate divisor latch for COM1: set to 5555h, keyboardLEDs are flashed on and all keyboard toggles are set on. Int13requests with AH >= 3 are incremented by 1, making it difficult(amongst other things) to save data. Permanent: (see TRANSIENT_DAMAGE: above) |
| Damage Trigger: | Transient: Virus run twice on the 11 day of the month ANDInt_13 es:[bx+si] <= 78h (keyboard only affected if ss:[bx] <= 0C7h) Permanent: (see T_DAMAGE_TRIGGER: above) |
| Particularities: | The virus is not memory resident, but installs a resident payload. The virus resides at the memory address: 0:505 The first time it is run on the 11th day of the month, 40:15h isset to 55h, the next time it is run on the same day an int13 handler(240 bytes) is installed at 0:505h. Does nothing to cope with infecting read-only files, so in thatrespect it could be quite obvious. No filesize checking is done.All data references within the virus are made relative referenceswith a macro that calls a subroutine to get the value of $+3 andthen adds DATA-$-3 to get the runtime address of the data in theCS: segment. One such reference breaks the pattern and appears tobe coded by hand. |
| Similarities: | |
Agents | |
| Countermeasures: | |
| Standard means: | |
Acknowledgements | |
| Location: | Virus Test Center, University Hamburg, FRG |
| Classification by: | Adam David, Frisk Software International |
| Documentation by: | Adam David, Frisk Software International |
| Date: | 20.6.93 |
| Information Source: | Caroentry (autom.converter by S.Freitag) |
(c) 1996 Virus-Test-Center, University of Hamburg