Untrusted inbound list without an explicit logged deny
At a glance
Base severity
Area
Platform
Evidence level
Benchmark reference
Reads the export, not the device
ConfigProof reads a configuration export. This control is evaluated against the objects in that file, and it reports what the file says. It does not connect to the device and sees no traffic, so a finding here describes the configuration, not what the firewall is doing right now.
Why it matters
The implicit deny at the end of an ASA list logs nothing, so traffic refused from the internet side leaves no record.
How to fix it
Web interface
The steps below are written for the web interface. A finding raised on your own export carries the same steps with your object names filled in.
- In ASDM: Configuration > Firewall > Access Rules, add a last rule on the interface: Action Deny, Source any, Destination any, Service ip, Logging enabled. Apply and save.
- On the CLI: access-list <list> extended deny ip any any log, and write memory.
Command line
Cisco ASA CLI
configure terminalaccess-list <access-list> extended deny ip any any logendwrite memory
An example. Values in angle brackets are yours to supply; a finding on your own export fills in the names it read. Typed in configuration mode; write memory saves it, with no separate commit. Read every line first.
Read it back
show access-list <access-list>Values to fill in1
- <access-list>
- The access list
Before you type it2
- Written from the ASA 9.x command reference and not run on a device: read each line before you paste it.
- In multiple context mode, type it in the context it applies to (changeto context <name>).
How to confirm the fix
- Run show access-list <list> and confirm the last entry is deny ip any any log.
Limits
- No limitation is recorded for this control beyond the one that applies to all of them: it reads a configuration export.
Compliance references
CIS Cisco ASA 9.x Firewall Benchmark v1.1.0
Covers part of the recommendation
Where a control aligns with a recommendation of the CIS Cisco ASA 9.x Firewall Benchmark v1.1.0, that recommendation is cited as a reference. Only that version was checked. A reference is not a certification.
More in Security Policies
- ASA-SEC-001Inbound entry allows any destination or any service
- ASA-SEC-002permit ip any any entry
- ASA-SEC-005Entry covered by an earlier entry
- ASA-SEC-006Inactive entry left in a list
- ASA-SEC-009Remote administration, file sharing or database port open inbound
- ASA-SEC-022EtherType list permits any EtherType
See it on your own firewall
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