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Analyzing Azure Network Security Group Flow Logs

Reitse Eskens says the bits must flow:

I had an interesting question lately where I was requested to show all the network traffic within an Azure landing zone. Specifically source and target IP, protocol and port. From the aspect of Zero Trust, it’s important to show both successful and failed connections in your network. To be able to answer this question I had prepared myself by enabling the so-called flow logs on the Network Security Groups (NSG). NSG’s are used to control traffic on the IP and port level between resources. There’s no packet inspection, just a check if IP 1 is allowed to connect to IP 2 on port 3. In this specific case, it also had to do with a migration to Azure Firewall where all the NSG rules had to be validated.

But getting the data is one thing, finding out what is in it is something else. In this blogpost I’ll drag you along the steps I took to get the raw JSON data into a SQL table and analyse the data.

Read on for the process and quite a bit of T-SQL code.

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