Inspired by a post to the SANS Intrusions list, I have written `tattle` to automate the reporting of SSH brute-force attacks. `tattle` is a perl script that crawls through your sshd logs (/var/log/messages, or wherever you tell it to look) and finds hosts who've connected to your SSH server. All hosts who connect to your box, and that are not accounted for in the exception list, are reported to the point-of-contact for the domain the host is registered too (where available.) Long story-short, if you stick `tattle` in your cron-tab, you can automate the reporting of ssh brute-force attacks. If you're interested, you can download `tattle` from http://sodaphish.com/files/tattle (its also pasted to the end of this email.) Ciao, -C #!/usr/bin/perl # tattle by C.J. Steele, CISSP <coreyjsteele@xxxxxxxxx> # (C)opyright 2005, C.J. Steele, all rights reserved. # # NOTICE: you're on your own with whatever 'messes' reporting this sort of # activity may create...you've been warned. # # This script processes log files and attempts to automatically notify domain # authorities of machines in their domain that are actively performing SSH # brute-force attacks. Mangle the variables above the warning to your liking, # but it would be adviseable not to venture past the warning unless you know a # bit of perl and are comfortable doing so. # # use strict; use MIME::Lite; use File::MkTemp; my $logfile = "/var/log/messages"; #the place where ssh logs to my $tmpdir = "/tmp"; #for use when we write out our logs my @exceptions = ( "10.10.10.10", "your.net" ); #domains not to notify of ssh attacks, i.e. your domains my $smtp_host = "localhost"; #your mail server my $smtp_sendas = "your\@email.com"; #a VALID e-mail address to send the e-mails out as my $smtp_message = "An attempt to brute-force account passwords over SSH has been detected by a machine in your domain. Attached are logs indicating the times and dates of the activity. Please take the necessary action(s) to stop this activity. If you have any questions, please reply to this email or contact me at $smtp_sendas."; #the nasty-gram ######################################################################## # DO NOT MUCK AROUND BELOW THIS POINT UNLESS YOU KNOW WHAT YOU'RE DOING ######################################################################## my @offenders = getoffenders( $logfile ); foreach my $offender ( @offenders ) { my $tld = gettld( $offender ); my @addies = getemails( $tld ); if( scalar( @addies ) ) { my $logpath = writelogs( getlogs( $offender ) ); foreach my $addie ( @addies ) { #create the email... my $email = MIME::Lite->new( From => "$smtp_sendas", To => "$addie", Cc => "$smtp_sendas", Subject => "SSH Brute-force Attack", Type => "TEXT", Data => "$smtp_message" ); #attach our log files/evidence... $email->attach( Type => 'text/plain', Path => $logpath, Filename => "$offender.txt" ); $email->send( 'smtp', "$smtp_host" ); print "I: e-mail sent to $addie ($offender)\n"; } #end foreach } else { print "E: no e-mail addresses found for $tld\n"; } #endif } #end foreach exit( 0 ); sub getlogs # this routine parses the log file and finds entries that match the $mark, # which is passed in as a parameter, and creates an array, each element of # which is a matching line of the log, the single array is returned. { my $mark = shift; my @logentries = (); open( LOG, $logfile ) or die( "$!" ); while( <LOG> ) { chomp(); if( $_ =~ /$mark/ ) { push( @logentries, $_ ); } #endif } #end while close( LOG ); return @logentries; } #end getlogs() sub writelogs # this writes the array of log entries passed via args to a randomly created # temporary file, the name of which is returned as a single scalar value, with # fully-qualified path. { my @logs = @_; my $tmpfile = mktemp( "$tmpdir/rptbdgys.XXXXXX" ); open( OUT, ">$tmpfile" ) or die( "$!" ); foreach( @logs ) { print OUT $_, "\n"; } close( OUT ); return $tmpfile; } #end writelogs sub getoffenders # this returns an array of offending hostnames from the logfile, except those # who are listed in the @exceptions array. { my $log = shift; my @offs; open( LOG, $log ) or die( "$!" ); while( <LOG> ) { chomp( $_ ); if( $_ =~ /sshd/ and $_ =~ /rhost/ ) { my @e = split( /\s/, $_ ); my $off = $e[12]; $off =~ s/rhost\=//; $off =~ s/ruser\=//; #why do I need this? if( $off ne "" ) { push( @offs, $off ) if( ! isin( $off, @offs ) and ! isin( $off, @exceptions ) ); } #endif } #endif } #endwhile close( LOG ); return( @offs ); } #end getoffenders() sub gettld # this returns a single scalar value containing the top-level domain or # the ip address fed in. This won't work for a site who's address is # dom.com.co { my $in = shift; if( $in =~ /[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*/ ) { # its an IP address... try reverse lookup, if that fails, return IP return $in; } else { # its a hostname my @bits = split( /\./, $in ); my $bitslen = scalar( @bits ); if( $bitslen > 2 ) { if( length( $bits[$bitslen-1] ) == 2 ) { # country-level tld if( length( $bits[$bitslen-2] ) > 3 ){ return "$bits[$bitslen-2].$bits[$bitslen-1]"; } else { return "$bits[$bitslen-3].$bits[$bitslen-2].$bits[$bitslen-1]"; } #endif } else { # tld return "$bits[$bitslen-2].$bits[$bitslen-1]"; } #endif } else { return $in; } #endif } #endif } #end gettld() sub getemails # gets a list of unique email addresses that were returned for as part # of the domain's `whois` records. The results are returned as a # singular array. { my $tld = shift; my $whois = `/usr/bin/whois $tld`; my @emailaddies; foreach( split( /\n/, $whois ) ) { chomp(); if( $_ =~ /[a-zA-Z0-9]*\@[a-zA-Z0-9]*/ ) { # the line had an e-mail address in it... my @bits = split( /\s/, $_ ); foreach my $bit ( @bits ) { if( $bit =~ /[a-zA-Z0-9]*\@[a-zA-Z0-9]*/ and $bit !~ /\@apnic\.net$/ ) { push( @emailaddies, $bit ) if( ! isin( $bit, @emailaddies ) ); } #endif } #end foreach } #endif }#end foreach return @emailaddies; } #end getemails sub isin # this boolean function simply checks to see if an element ($e) is in the # supplied array (@a) -- it returns 1 if the element is in the array and 0 # otherwise. { my( $e, @a ) = @_; foreach( @a ) { return 1 if( $e eq $_ ); } return 0; } #end isin() -- C.J. Steele, CISSP <coreyjsteele@xxxxxxxxx>
