Hi William, Again, if you run NetMon for three seconds and look at the decodes, you should be able to figure it out. You'll see a lot of SMTP traffic and DNS traffic that doesn't look quite right. Putting together those findings with SMTP server logs, DNS server logs, the ISA firewall logs, will help solve this problem. You can use a tool like Packetyzer to make things a bit easier. HTH, Tom www.isaserver.org/shinder Get the book! Tom and Deb Shinder's Configuring ISA Server 2004 http://tinyurl.com/3xqb7 MVP -- ISA Firewalls -----Original Message----- From: William Robertson [mailto:robertson.william@xxxxxxxxxxxxxx] Sent: Wednesday, August 18, 2004 12:47 AM To: [ISAserver.org Discussion List] Subject: [isalist] RE: OT: Tool to identify Evaluate DNS clients? http://www.ISAserver.org Thanks Tom, unfortunately I don't have Exchange, I've only got a Linux SendMail server - with very limited options regarding the control of mail etc. You got a good point though - I do believe the problem is a symptom of bogus addresses being queried against my DNS server and then just causing an inherent DoS. The problem is trying to find the culprit that is causing this problem... I'll try again and look into the Packet Sniff's, was just hoping that someone out there may have heard of some reporting utility that could assist with aggregating the DNS logs or something. Anyway, thanks again, Cheers William R. -----Original Message----- From: Thomas W Shinder [mailto:tshinder@xxxxxxxxxxx] Sent: 17 August 2004 04:36 PM To: [ISAserver.org Discussion List] Subject: [isalist] RE: OT: Tool to identify Evaluate DNS clients? http://www.ISAserver.org Hi William, Could be something that I saw not too long ago on my own corpnet. Is your Exchange Server getting flooded with bogus destination e-mail addresses? The NDR and notification messages might be trying to resolve bogus domain names. Turn off NDR and notification messages and it will stop. Check your queues and badmail folders to confirm. HTH, Tom www.isaserver.org/shinder Get the book! Tom and Deb Shinder's Configuring ISA Server 2004 http://tinyurl.com/3xqb7 MVP -- ISA Firewalls -----Original Message----- From: William Robertson [mailto:robertson.william@xxxxxxxxxxxxxx] Sent: Tuesday, August 17, 2004 8:36 AM To: [ISAserver.org Discussion List] Subject: [isalist] RE: OT: Tool to identify Evaluate DNS clients? http://www.ISAserver.org Hmmm, tried to avoid saying that... what I am seeing is that my internet link is saturated with outbound DNS requests. In my Firewall Logs I can only see my 2 DNS servers as doing the requests for outbound DNS queries, which is the way it is meant to be... But what I am presuming is that some client workstation is generating/causing a helluva lot of DNS requests, either via directly contacting my DNS Server, or by requesting Port 80 traffic which will then route via my Firewall to my DNS Server, and then back through my firewall. So I was hoping to tackle the easier scenario first, and hoping to generate some sort of realtime/historical report which will show me the "Top Requesters" for DNS resolution against my DNS Servers... Is there something like this? -----Original Message----- From: Thomas W Shinder [mailto:tshinder@xxxxxxxxxxx] Sent: 17 August 2004 03:24 PM To: [ISAserver.org Discussion List] Subject: [isalist] RE: OT: Tool to identify Evaluate DNS clients? http://www.ISAserver.org Hi William, Are you saying that the ISA firewall is generating a lot of DNS traffic? Thanks! Tom www.isaserver.org/shinder Get the book! Tom and Deb Shinder's Configuring ISA Server 2004 http://tinyurl.com/3xqb7 MVP -- ISA Firewalls -----Original Message----- From: William Robertson [mailto:robertson.william@xxxxxxxxxxxxxx] Sent: Tuesday, August 17, 2004 6:11 AM To: [ISAserver.org Discussion List] Subject: [isalist] OT: Tool to identify Evaluate DNS clients? http://www.ISAserver.org Hi there I seem to be experiencing an extreme amount of outbound DNS requests via my FIREWALL to my local DNS Servers. I am quite confident that this traffic is not legitimate and is most likely the source of an *evil* application ;) Does anyone know if it is at all possible to "query" a Win2K DNS Server to see which clients are in fact making the DNS requests? I.e. I want to be able to see which PC is at the top of the list with regards the number of queries, or at least see which "dodgy" domain names are being requested from which PC's... Any ideas? 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