RE: DoS attack from java connections - how to avoid

  • From: D'Hooge Freek <Freek.DHooge@xxxxxxxxx>
  • To: "John.Hallas@xxxxxxxxxxxxxxxxxx" <John.Hallas@xxxxxxxxxxxxxxxxxx>, oracle_l <ORACLE-L@xxxxxxxxxxxxx>
  • Date: Tue, 31 Aug 2010 17:58:41 +0200


These "dead" processes, are they processes on the db server or on the 
application server?
In neither case it seems normal to me that a process keeps existing after a 
failed connection attempt, but if this is on the db server you can try if 
enabling dead client detection (sqlnet.expire_time) would help in cleaning up 
those processes.


Freek D'Hooge
Oracle Database Administrator
email: freek.dhooge@xxxxxxxxx
tel +32(0)3 451 23 82
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of John Hallas
Sent: dinsdag 31 augustus 2010 11:07
To: oracle_l
Subject: DoS attack from java connections - how to avoid

We had an application that repeatedly connects to the database via java 
connection pool fail because the account had become locked. 
The application kept on trying, the database did not allow the connection and 
we ended up with thousands of 'dead' processes causing the unix server to hang 
as all memory was used up.

The obvious thing to fix in our case was some form of application logic to 
recognise that failed connections had been made and stop the repeated 
connection attempts.

However this could also be used in a denial of service attack. What steps could 
we take to reduce that risk. The problem as I see it is that the database has 
reacted correctly and there is not much more we could do at the database level. 
However I am always open to suggestions


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