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Strange packets

I have a system which appears to be sending packets to 223.1.128, which sounds like a Sonicwall VPN address (per stuff found on the internet) - but there is no sonicwall software installed on the box.  It fires from TCP port 139 to a random destination port in the 1000-1500 range.

It happens very regularly - but not exact - at about 20 second intervals.

Netstat shows no reference to a 223 address (netstat -abnv | find "223")

Thoughts?  Any idea on how to track such an animal down?
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Does IPCONFIG report on Virtual Adapters as for Sonicwall ?
Port 139 is used for Netbios session service but also from virus/trojan [1]. Did you scan your computer ?

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There are no Sonicwall virtual adapters on this machine; there is no virus on the machine, either.

I ran TCPView yesterday, and it *doesn't* show the target IP address at all.  I began to wonder if another machine might be spoofing the data; I installed Wireshark on the machine to capture network data.

All of a sudden, I saw a packet *INBOUND* that purported to be *FROM*; there was no TCP handshake taking place, which is why (I think) TCPView didn't show anything.

My next step is to track the MAC address, which is a Cisco address - I believe that the originator of the bogus packet is on a different subnet/VLAN, and so the MAC in the packet captured is going to match the internal MAC of one of my switches.

I did notice yesterday on TCPView that just before the packet goes out to, that a packet comes in from a specific machine.  I'm wondering if that machine is generating packets purporting to be  I'm checking it out.

Other suggestions?
I agree. Checking the destination MAC address of the inbound packet from, will allow you to understand which machine is going to receive the packet. That should be the one that is generating the outbound traffic as well, but in case of something anomalous, that's not mandatory.

Can you monitor the router outbound gtraffic ? Can you block the outbound traffic ? That would help to verify if the problem is generated internally to LAN/WAN.
Sounds like you are onto something. I would check the specific machine that is sending these packets. It
may have a virus or other software installed that is causing this.