Virus Database

Freew

Description Freew

It's very dangerous not memory resident virus which searches for .COM-files (except COMMAND.COM) and writes itself into their beginnings. It contains the text strings: "Freew", ".. *.* *.com COMMAND.MKS_VIR.". It can overwrite the files by a small program which types "Program terminated normally" and returns to DOS.

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Cascade.1491

Description Cascade.1491

This is a memory resident virus. Its body except for the beginning (first 32 bytes) is encoded. As a key the length of the infected file is used. That is why two strains of the same virus in most cases will coincide only in the first 32 bytes.
As an infected program is executed, the control of the JMP command is transferred to the beginning of the virus. By first commands the virus determines the length of the source file and deciphers its body.
On creating its memory-resident copy the virus:
copies its body into the highest addresses of the memory;
moves the body of the main program into the highest addresses of the memory;
moves the virus body into cleared area above the main program body;
sets INT 1Ch, 21h, 28h to its own copy.
ƒ all ƒ ƒ ... ƒ ƒ ... ƒ ƒ ... ƒ
+---------ƒ +---------ƒ +---------ƒ +---------ƒ
ƒProgram ƒ ƒProgram ƒ--+ ƒFree ƒ +-->ƒVirus ƒ
ƒ ƒ ƒ ƒ ƒ ƒmemory ƒ ƒ ƒ ƒ
ƒ ƒ ƒ ƒ ƒ +---------ƒ ƒ +---------ƒ
+---------ƒ +---------ƒ +-->ƒProgram ƒ ƒ ƒProgram ƒ
ƒVirus ƒ--+ ƒVirus ƒ ƒ ƒ ƒ ƒ ƒ
ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ
+---------ƒ ƒ +---------ƒ +---------ƒ ƒ +---------ƒ
ƒ ... ƒ +-->ƒVirus ƒ ƒVirus ƒ--+ ƒ ... ƒ
ƒ(copy) ƒ ƒ ƒ
+---------ƒ +---------ƒ
ƒ ... ƒ ƒ ... ƒ

The virus affects only COM files as it's loaded into the memory for execution. Infection is carried out by standard method. Most widely spread versions of this virus does not reinfect files.
The virus changes interrupt vectors 1Ch, 21h and 28h. It also produces a specific video-effect: crumbling down of letters on the screen; does not have destructive functions.
Sometimes it displays the message:
IL SISTEMA è FOTTUTO!!
S.E.K. VIRUS Made in ITALY RM
5iD G.Ferraris 90/91 (c)
Then it erases the disk sectors. It also deletes CHKLIST.CPS file.

Cascade.691

Description Cascade.691

This is a memory resident virus. Its body except for the beginning (first 32 bytes) is encoded. As a key the length of the infected file is used. That is why two strains of the same virus in most cases will coincide only in the first 32 bytes.
As an infected program is executed, the control of the JMP command is transferred to the beginning of the virus. By first commands the virus determines the length of the source file and deciphers its body.
On creating its memory-resident copy the virus:
copies its body into the highest addresses of the memory;
moves the body of the main program into the highest addresses of the memory;
moves the virus body into cleared area above the main program body;
sets INT 1Ch, 21h, 28h to its own copy.
ƒ all ƒ ƒ ... ƒ ƒ ... ƒ ƒ ... ƒ
+---------ƒ +---------ƒ +---------ƒ +---------ƒ
ƒProgram ƒ ƒProgram ƒ--+ ƒFree ƒ +-->ƒVirus ƒ
ƒ ƒ ƒ ƒ ƒ ƒmemory ƒ ƒ ƒ ƒ
ƒ ƒ ƒ ƒ ƒ +---------ƒ ƒ +---------ƒ
+---------ƒ +---------ƒ +-->ƒProgram ƒ ƒ ƒProgram ƒ
ƒVirus ƒ--+ ƒVirus ƒ ƒ ƒ ƒ ƒ ƒ
ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ
+---------ƒ ƒ +---------ƒ +---------ƒ ƒ +---------ƒ
ƒ ... ƒ +-->ƒVirus ƒ ƒVirus ƒ--+ ƒ ... ƒ
ƒ(copy) ƒ ƒ ƒ
+---------ƒ +---------ƒ
ƒ ... ƒ ƒ ... ƒ

The virus affects only COM files as it's loaded into the memory for execution. Infection is carried out by standard method. Most widely spread versions of this virus does not reinfect files.
The virus changes interrupt vectors 1Ch, 21h and 28h. It also produces a specific video-effect: crumbling down of letters on the screen; does not have destructive functions.

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