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iptables / OS firewall rule to block scanning on Tcp/Udp 53, Tcp2381 for PHP & Openssh Tcp22

Posted on 2015-01-03
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Last Modified: 2015-01-20
Will creating iptables / firewall rule to permit only selected sysadmin laptops (or app servers) to
access vulnerable servers (ISC Bind on Tcp/Udp 53 & PHP Tcp2381 & Openssh's too old versions)
help to block VA scanner's detection.

To help with mitigation till we have the resource to upgrade to higher versions
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Question by:sunhux
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by:gheist
gheist earned 100 total points
ID: 40529369
Each of services has their IP-based access lists. And their ways of support to actually install updates (once a year before VA scan if no better idea)
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Schuyler Dorsey earned 400 total points
ID: 40551426
Well. You're attacking a symptom and not the problem. You should NOT change ACL rules to prevent a vulnerability scanner from reaching a service on a host. If anything vulnerability scanners need to have blanket access to every port on every host.

Regardless of whether or not you adjust the ACL, the risk exists. If you change the ACL to prevent the scanner from hitting the port, you are hiding the risk, not acting on the risk. And thus you would not be able to report correctly on the risk.

Now, adjust the ACL to restrict access is certainly a remediation control you could use to act up on the present risk. So I agree with your approach only if you also add an ACL item which continues to allow the vulnerability scanner full access to the vulnerable servers.
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by:gheist
ID: 40559565
Recomendation:
Update BIND (If out of redhat support you buy it or roll over to CentOS) - old 9-series configuration will work just fine, named-checkconf -z is your friend.
PHP TCP 2381 is HP management server - upgrade it (it is called SMH) at the same time restricting access or even binding it to localhost.
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