Cisco ASA5505 How to Block IP from internet access not internal resources VIA ASDM 6.4

This would be done with an ACL applied to the inside interface.  Assuming the ACL is called inside_access_in the command to block 10.10.10.10 from the internet would be

access-list inside_access_in extended deny ip 10.10.10.10 255.255.255.255 any
access-group inside_access_in in interface inside

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If you have multiple subnets on your internal network and the ASA is your default gateway you might need a couple permit lines in front of the deny line.  Let's say 10.10.10.10 is on 255.255.0.0 subnet and you also have 10.20.0.0/16 and 10.30.0.0/16 networks they need to reach.

access-list inside_access_in extended permit ip 10.10.10.10 255.255.255.255 10.20.0.0 255.255.0.0
access-list inside_access_in extended permit ip 10.10.10.10 255.255.255.255 10.30.0.0 255.255.0.0
access-list inside_access_in extended deny ip 10.10.10.10 255.255.255.255 any
access-group inside_access_in in interface inside

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Via the ASDM

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This would stop my internal IP address 10.254.254.113 from getting to the outside of the firewall.

Here You go, I've written it up for you.

Cisco ASA 5500 - Deny a Single IP Address External Access



Pete