Snort mailing list archives

inline advice


From: Dev Null <dev.null () BeginThread com>
Date: Thu, 23 Aug 2007 10:31:45 -0500

We've setup snort on a dedicated box that plays router in front
of a group of web servers and colocation boxes. We've ssh port-forwarded
mysql back to a dedicated mysql box, and we're using BASE to wade
(literally) through the alerts.

Our intention is to (a) whittle down on the rules and then (b) switch to
inline and have snort drop packets that the rules catch. We're in the
"whittle" phase right now.

Any links or documentation on (a) this type of setup or (b) whittling
down on the rules would be greatly appreciated.

Immediately after starting up snort we were bombarded with a lot of port
scan alerts coming from some of the internal mail servers and servers
that use http to grab updated information. It seems odd that snort would
trigger this normal activity as port scanning, when it doesn't flag
other servers/users connecting to our internal servers to request web
pages or send email. We researched a handful of the alerts and found
that they are indeed false positives. Can someone clarify why snort
would think our server making normal outbound connections would be
flagged as port scanning?

We added our internal server range of IPs to the ignore_scanners option
of sfportscan, and that certainly cut down on those false positives, but
we don't want to leave it like that, if one of our colocation clients
were port scanning we wouldn't know it.

Thanks in advance for all your help and advice.


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