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Date:      Tue, 1 Jan 2002 16:29:15 -0500
From:      "Joe & Fhe Barbish" <barbish@a1poweruser.com>
To:        "Joe Clarke" <marcus@marcuscom.com>
Cc:        "FBSD Questions" <questions@FreeBSD.ORG>
Subject:   RE: IPFW UDP port# 520
Message-ID:  <LPBBIGIAAKKEOEJOLEGOMEPECKAA.barbish@a1poweruser.com>
In-Reply-To: <1009907433.16477.4.camel@shumai.marcuscom.com>

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This machine is a virgin install of FBSD never been connected to 
the internet without firewall. There's no way that the Ripper 
Trojan could have infested my box. The 520's I am receiving can 
Only be from my ISP's router. 

What ipfw rules do I need to respond to make that router 
happy and shut up?


-----Original Message-----
From: Joe Clarke [mailto:marcus@marcuscom.com]
Sent: Tuesday, January 01, 2002 12:50 PM
To: Joe & Fhe Barbish
Cc: FBSD Questions
Subject: Re: IPFW UDP port# 520

On Tue, 2002-01-01 at 12:22, Joe & Fhe Barbish wrote:
> Happy new year to all FBSD list readers.
>
> I see in my security log a lot of denied packets over and
> over again of the same kind.
>
> Deny UDP 208.203.25.3:520 63.163.61.14:520 in via tun0
>
> 208.203.25.3 is my ISP's IP address and 63.163.61.14 is my IP address.
>
> When I lookup what port 520 is it says a local routing process
>  or  Trojan Ripper.  I think it's my ISP's front door router
> inquiring if I am still there.
> Since my firewall is denying the request it just keeps repeating.
>
> How can I be sure It's my ISP's router and not the Ripper Trojan?

I've never seen udp/520 used as a trojan port.  In fact, Trojans are
usually booby-trapped programs that lie around waiting for someone to
use them.  I don't know what a trojan UDP port would be.

Chances are, this is your ISP's router trying to talk RIP with you.
While I can't imagine a big ISP using RIP anymore, it's certainly
possible.

>
> What rules do I need the add to my IPFW rules set to resolve this?

If you're really nervous about this, make sure nothing is listening on
udp/520 (i.e. turn off routed or gated), and allow the packets through
for a short time.  Put a sniffer on the interface, and see if it
recognizes the packets as RIP.  RIP is defined by RFC1058, so you can
compare the message formats and see what those packets are trying to
do.  It might be just advertising a 0.0.0.0 default route to you.

Joe

>
> Thanks
>
> Joe
>
>
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