On the BIND 9.x server, the private keys corresponding to both the zone signing key (ZSK) and the key signing key (KSK) must not be kept on the BIND 9.x DNSSEC-aware primary authoritative name server when the name server does not support dynamic updates.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-272385	SRG-APP-000516-DNS-000112	BIND-9X-001280	SV-272385r1124044_rule	2025-07-24	3

Description
The private keys in the KSK and ZSK key pairs must be protected from unauthorized access. If possible, the private keys should be stored offline (with respect to the internet-facing, DNSSEC-aware name server) in a physically secure, nonnetwork-accessible machine along with the zone file primary copy. This strategy is not feasible in situations in which the DNSSEC-aware name server has to support dynamic updates. To support dynamic update transactions, the DNSSEC-aware name server (which usually is a primary authoritative name server) has to have both the zone file primary copy and the private key corresponding to the zone-signing key (ZSK-private) online to immediately update the signatures for the updated RRsets. The private key corresponding to the key-signing key (KSK-private) can still be kept offline.

Description

The private keys in the KSK and ZSK key pairs must be protected from unauthorized access. If possible, the private keys should be stored offline (with respect to the internet-facing, DNSSEC-aware name server) in a physically secure, nonnetwork-accessible machine along with the zone file primary copy. This strategy is not feasible in situations in which the DNSSEC-aware name server has to support dynamic updates. To support dynamic update transactions, the DNSSEC-aware name server (which usually is a primary authoritative name server) has to have both the zone file primary copy and the private key corresponding to the zone-signing key (ZSK-private) online to immediately update the signatures for the updated RRsets. The private key corresponding to the key-signing key (KSK-private) can still be kept offline.

ℹ️ Check
Determine if the BIND 9.x server is configured to allow dynamic updates. Review the "named.conf" file for any instance of the "allow-update" statement. The following example disables dynamic updates: allow-update {none;}; If the BIND 9.x implementation is not configured to allow dynamic updates or inline signing, verify with the system administrator (SA) that the private ZSKs and private KSKs are stored offline. If not, this is a finding.

ℹ️ Check

Determine if the BIND 9.x server is configured to allow dynamic updates. Review the "named.conf" file for any instance of the "allow-update" statement. The following example disables dynamic updates: allow-update {none;}; If the BIND 9.x implementation is not configured to allow dynamic updates or inline signing, verify with the system administrator (SA) that the private ZSKs and private KSKs are stored offline. If not, this is a finding.

✔️ Fix
Remove any ZSK or KSK private key from any BIND 9.x server that does not support dynamic updates. Note: Any ZSK or KSK that is not needed to support dynamic updates must be stored offline in a secure location.