How to address a spike in TCP and UDP flows

Have an unusual spike in TCP and UDP flows? Expert Peter Wood explains how to zero in on the problem.

I noticed an unusual spike in TCP and UDP flows from a single internal source to multiple destinations. What steps you would take to determine the type of traffic that this represents?
To address a spike in TCP and UDP flows, run a packet sniffer such as Wireshark or CommView on a hub connected to the target device. Both these programs give you the opportunity to filter traffic during capture and post-capture to determine what is going on. Filters can be set for individual ports or protocols, as well as source and destination IP addresses. You can also rebuild sessions using either of these tools. If the device is non-critical, you may wish to isolate it first, in case it has been infected with malware.

This was first published in October 2009



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