Part 1: Blocking Bad Hosts – Finding Them, Easily

Download Script:

While troubleshooting some issues on an OWA Front-End server, I went over to the security log to see if the authentication attempts were getting past this box. The problem I found was the log was so full of failed logon attempts it was difficult to filter out what I was looking for. In a twelve hour period, there were thousands of 529 events in the security log. Now, I know this is nothing new, but I found a few patterns. I manually exported the log to a CSV, parsed out all the source ip addresses and opened it up in Excel. What I found was that 98.7% of failed logon attempts were made by just four different ip addresses.  (I recommend using MaxMind’s GeoIP Address Locator for help in determining where the source addresses are located.) Read More