News Group Posts

email worm management

From: Jean-Pierre Radley <jpr@jpr.com>
Subject: Re: How Can I Block Latest Worm-Generated SPAM?
Date: 19 Sep 2003 16:11:00 -0400
References: <Pine.UW2.4.21.0309191413380.24405-100000@ris7.UniXpress.com> 

Lucky Leavell typed (on Fri, Sep 19, 2003 at 06:21:32PM +0000):
| I know I am one of very many hapless souls receiving message after message
| totaling around 150K/message purporting to be M$ patches or undeliverable
| or some such muck. When receiving similar SPAM generated by SoBig.F, it
| all (for me) came from one IP address so it was fairly easy to insert a
| statement in my .maildelivery file to eliminate it but today's has no
| discernible pattern I can see.
| 
| Any suggestions on how to stem the flow other than closing port 25 which
| would only defer the problem? My email server is UW7.1.0 with PTF7130e
| installed. I even though about rejecting any messages with attachments but
| am not sure how to do that with sendmail.
| 
| The main headache it is causing me today is that it takes so much of my
| very limited bandwidth that the only thing I can do is send
| (hopefully!) and receive (definately!) email.  Everything else, including
| pings time out with Unknown Host.

I hate sendmail and run smail here.  It pipes incoming main to Chip
Salzenburg's 'deliver'; ~part~ of my /usr/local/lib/deliver.sys reads:

 #!/bin/ksh
 # /usr/local/lib/deliver.sys
 # 1.4  JPR  18Sep03
 
 typeset -l TO=`header -f To -f Cc -f Apparently-To -f Sender $HEADER`
 ID=`header -f Message-ID $HEADER`
 typeset -l FR=`header -f From $HEADER | sed '
 s/.*<\(.*\)>.*/\1/
 s/[("].*[)"]//
 s/ //g'`
 typeset -l CT=`header -f Content-Type $HEADER | sed 's/;.*//'`
 typeset -l CN=`header -f Control $HEADER`
 IP=`header -f Received $HEADER | sed -n '1s.*\\[\\(.*\\)].*\\1p'`
 : ${IP:=localhost}
 USER=$1
 
 # Configure the email server to block or remove email that contains file
 # attachments that are commonly used to spread viruses, such as .vbs, .bat,
 # .exe, .pif and .scr files.
 
 for X in EXE BAT PIF SCR VBS
 do
  grep -iq "^Content-.*name=.*\.$X" $BODY &&
  echo "A .$X file mailed by $FR\nto $TO\nvia $IP\nwas dumped in the garbage."|
        mutt -s "Dumped .$X file" $USER &&
        /usr/local/bin/addfilter $IP &&
        echo DROP &&
        exit
 done

/usr/local/bin/addfilter collects IP addresses which an overnight cron
job adds to my local RBL list.

-- 
JP

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