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What triggers a port scan attack



Article ID: KB5106 KB Last Updated: 09 Jun 2010Version: 3.0
What triggers a port scan attack
There is a threshold setting in the WebUI, but no unit shown What triggers a port scan attack

Port scanners try to connect to a remote host by attempting to connect to all ports on the host.  If the port scan responds to any of those attempts, it will create a log so that the hacker can investigate any holes to attack.
Host applications will usually listen on a small set of specific ports on TCP.  However, other ports on the server may also be active.  This is a definite vulnerability, and hackers will employ a port scan, and check for any unprotected port, and could launch an attack on the server using that unprotected port.
NetScreen includes an option to detect a port scan attempt, and block those packets.  NetScreen  internally logs the number of different ports from one remote source to one destination.  The port scan threshold is set to a default of 10 ports scanned per 5000 microseconds, which equates to 2000 ports/second.  Increasing the port scan threshold will increase the likelihood of a positive port scan detection. 

Here is the problem or goal:

  • What triggers a port scan attack

Problem Environment:

  • There is a threshold setting in the WebUI, but no unit shown

Applicable Products:

  • NetScreen-5
  • NetScreen-5XP
  • NetScreen-10
  • NetScreen-25
  • NetScreen-50
  • NetScreen-100
  • NetScreen-204
  • NetScreen-208
  • NetScreen- 500
  • NetScreen-1000

Applicable ScreenOS:

  • 1.64
  • 1.65
  • 1.66
  • 2.00
  • 2.01
  • 2.10
  • 2.50
  • 2.6.0
  • 2.6.1
  • 2.7.1
  • 2.8.0
  • 3.0.0
  • 3.0.1
  • 3.0.2
  • 3.1.0

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