[leafnode-list] filtering spam articles using the "from" field

[Mark]

There is a lot of spam lately that has names in the "from" field such as

jamiescot at su.shawcable.net
deanmartin at wk.shawcable.net
peterreid at vs.shawcable.net

The name and address always changes, however the last part of the 
address is always .shawcable.net.

Is there any way to create a leafnode filter that will reject all posts 
based on the .shawcable.net.

Example headers, (I have removed the subject lines so this email clears 
my smtp filters)

 From - Fri Apr 23 07:18:23 2004
X-Mozilla-Status: 0001
X-Mozilla-Status2: 00000000
Path: pd7tw1no!pd7cy2so!shaw.ca!pd7tw2no.POSTED!53ab2750!not-for-mail
Message-ID: <wO8ic.235731$Ig.216728 at pd7tw2no>
From: peterreid at vs.shawcable.net
Newsgroups: 
alt.os.linux.mandrake,alt.os.linux.slackware,alt.os.linux.storm,alt.os.linux.suse,alt.os.linux.turbolinux,alt.os.macos,alt.os.macos.fight-back-for-the-mac,alt.os.multics,alt.os.nachos
Date: Fri, 23 Apr 2004 13:24:44 GMT
Lines: 4
X-Trace-PostClient-IP: 24.87.150.136
NNTP-Posting-Host: 64.59.144.74
X-Complaints-To: abuse at shaw.ca
X-Trace: pd7tw2no 1082726684 64.59.144.74 (Fri, 23 Apr 2004 07:24:44 MDT)
NNTP-Posting-Date: Fri, 23 Apr 2004 07:24:44 MDT
Organization: Shaw Residential Internet
X-Received-Date: Fri, 23 Apr 2004 07:24:44 MDT (pd7tw1no)
Xref: greplinux.dyndns.org alt.os.linux.mandrake:99319 
alt.os.linux.slackware:33071 alt.os.linux.suse:44301


 From - Thu Apr 29 17:47:58 2004
X-Mozilla-Status: 0001
X-Mozilla-Status2: 10000000
Path: pd7tw1no!pd7cy1no!shaw.ca!pd7tw2no.POSTED!53ab2750!not-for-mail
Message-ID: <pMOjc.294879$Ig.32740 at pd7tw2no>
From: deanmartin at wk.shawcable.net
Newsgroups: 
comp.protocols.kermit.misc,comp.protocols.misc,comp.protocols.nfs,comp.protocols.novell,comp.protocols.pcnet,comp.protocols.ppp,comp.protocols.pup,comp.protocols.smb,comp.protocols.snmp
Date: Wed, 28 Apr 2004 13:58:45 GMT
Lines: 804
X-Trace-PostClient-IP: 24.71.4.194
NNTP-Posting-Host: 64.59.129.46
X-Complaints-To: abuse at shaw.ca
X-Trace: pd7tw2no 1083160725 64.59.129.46 (Wed, 28 Apr 2004 07:58:45 MDT)
NNTP-Posting-Date: Wed, 28 Apr 2004 07:58:45 MDT
Organization: Shaw Residential Internet
X-Received-Date: Wed, 28 Apr 2004 07:58:45 MDT (pd7tw1no)
Xref: greplinux.dyndns.org comp.protocols.smb:2550