#
# New syscheck event - Store agent name
#
type=Single
pattern= (\S+)->syscheck
ptype=regexp
desc=$0
action=create OSSEC_SYSCHECK; assign %agent $1

#
# Integrity checking - Store filename
#
type=Single
ptype=regexp
context=OSSEC_SYSCHECK
desc=$0
pattern=Integrity checksum changed for: '(\S+)'
action=assign %file $1;

#
# Integrity checking - New event for SingleWithScript (I can't use %vars with script directive)
#
type=Single
ptype=regexp
context=OSSEC_SYSCHECK
pattern=New md5sum is : '(\S+)'
desc=OSSEC: Filename: %file - md5sum: $1
action=event OSSEC: Filename: %file - md5sum: $1

#
# Integrity checking - Check againts Virustotal.com
#
type=SingleWithScript
desc=$0
ptype=regexp
context=OSSEC_SYSCHECK
pattern=^OSSEC: Filename: (\S+) - md5sum: (\S+)
script=/usr/local/bin/sec-virustotal $2 $1
action=none
action2=eval %a \
({	use Sys::Syslog; \
	openlog('sec-virustotal','','user'); \
	syslog('info', "%agent: File %file ($1) is tagged as VIRUS by virustotal.com"); \
	closelog; \
	1;  \
};); delete OSSEC_SYSCHECK

Save this file under /etc/sec directory (I used ossec.sec as filename). Then we must define a new ossec rule:

sec-virustotal
	VIRUS
	Virus Found!!

Be sure to use an unused id for your new rule. You can add a group directive for correlating with another event if you want. Before start SEC, we can change sec-virustotal script to scan only those files with a desired extension:

#!/usr/bin/perl

use strict;
my $virus_script = '/usr/local/bin/mhc';
my @extensions = qw/exe dll/; # Use * for all extensions
my $filename;
my $hash;
my $ext;
my @tmp;

if($#ARGV != 1) {
    print "usage: $0 md5hash filename\n";
    exit 100;
}

$filename = $ARGV[1];
$hash = $ARGV[0];
my @tmp=split(/\./,$filename);
$ext = lc($tmp[$#tmp]);

foreach (@extensions) {
    if($ext eq $_ || $_ eq '*') { # Extension found, scanning...
        my $res = qx/$virus_script --hash $hash --no-cache/;
        exit ($? >> 8);
    }
}
exit 0;

We can change @extensions variable to scan ‘.scr’ files, for example. Now we have our new rule, restart ossec and launch SEC:

 # /var/ossec/bin/ossec-control restart
 # /usr/bin/perl -w /usr/bin/sec -conf=/etc/sec/ossec.sec -quoting -input=/var/ossec/logs/alerts/alerts.log -detach

I leave to the reader the step of launching SEC at startup. But for Debian edit /etc/default/sec:

#Defaults for sec
RUN_DAEMON="yes"
DAEMON_ARGS="-conf=/etc/sec/ossec.sec -input=/var/ossec/logs/alerts/alerts.log -pid=/var/run/sec.pid -detach -quoting"

I hope you find this useful.

he creado una versión del script que consulta virustotal.com desde la línea de comando, aunque lo he diseñado para que pueda ir integrando otros buscadores. De esta idea, nace Malware Hash Checker. Podéis descargarlo desde http://code.google.com/p/virtualminds/

Espero vuestros comentarios y sugerencias

Esta es cosecha propia

sub wc {
	my $words = shift;

	$words =~ s/[;|,|\.|\:|\?|\!|\/|\)|\=]/ /g;
	$words =~ s/\s{2,}/ /g;
	return scalar split(/ /,$words);
}

Visto en http://askville.amazon.com/find-code-sample-Perl-word-count-script/AnswerViewer.do?requestId=1037856

#!/usr/bin/perl
use strict;
use warnings;

my %count_of;
while (my $line = <>) { #read from file or STDIN
foreach my $word (split /\s+/, $line) {
$count_of{$word}++;
}
}
print "All words and their counts: \n";
for my $word (sort keys %count_of) {
print "'$word': $count_of{$word}\n";
}

Visto en http://dada.perl.it/shootout/wc.perl.html

use strict;

my($nl, $nw, $nc);

while() {
    $nc += length;
    $nw += scalar(split);
    $nl += 1;
    # print "$nl $nw $nc\n";
}
print "$nl $nw $nc\n";
exit(0);
while (read(STDIN, $_, 4095)) {
    $_ .= ;
    $nl += scalar(split(/\n/));
    $nc += length;
    $nw += scalar(split);
}
print "$nl $nw $nc\n";

– La forma más completa: http://folk.uio.no/einarro/Comp/download.php?file=texcount.pl
– Otro más: http://foundationstone.com.au/HtmlSupport/WebPage/wordcount.html
– Y otro con explicaciones: http://en.literateprograms.org/Word_count_(Perl)

Vamos a ponernos en faena. Apache tiene una directiva para definir variables de entorno en función de una serie de condiciones. Me refiero a la directiva SetEnvIf. Para nuestro ejemplo también nos valdría BrowserMatch pero opté por la primera por ser más genérica. Simplificaré un poco el montaje (mi cliente tenía varios dominios virtuales). En nuestro caso lo vamos a hacer con mi dominio, por ejemplo.

Lo primero que tenemos que hacer es abrir el fichero donde definimos nuestro virtualhost. Sobre la línea que define el CustomLog escribimos:

SetEnvIf User-Agent bot is_a_robot
CustomLog /var/log/apache2/robots_access.log combined env=is_a_robot

Estas dos líneas sirven para definir la variable is_a_robot y activar el log en caso de que esa variable de entorno exista (con el tipo de log combined)

#!/usr/bin/perl

#
# Iñaki Rodriguez (2007)
#
# Split robots in separate files (using md5 as filename)
#
# License: GPL

use Digest::MD5 'md5_hex';

my $robot_log = '/var/log/apache2/robots_access.log';
my $output_dir = '/var/log/apache2/robots/';
my %bots;

open BOTLOG, "<$robot_log" or die ("$robot_log: I can't open it");
open INDEX, "<".$output_dir."index.txt";

while() {
    chomp();
    my ($md5,$ua) = split(/\t/);
    $bots{$md5} = $ua;
}
close(INDEX);

while() {

    chomp();
    m/^(.+?) (.+?) (.+?) (\[.+?\]) (".+?") (\d\d\d) (.+?) (".+?") (".*")$/;
    my $md5 = md5_hex($9);
    my $tmpf = $output_dir.$md5.".log";
    open LOG,">> $tmpf" or die ("$tmpf: I can't write it");
    print "Adding entry to $tmpf ($9)\n" if ($ARGV[0] ne '-q');
    $bots{$md5} = $9 if (!$bots{$md5});
    print LOG $_."\n";
    close(LOG);
}

close(BOTLOG);

open INDEX, ">".$output_dir."index.txt" or die($output_dir."index.txt: I can't create it");
foreach $md5 (keys %bots) {
    print INDEX $md5."\t".$bots{$md5}."\n";
}
close(INDEX);