Explanation

Security Intelligence Sources ... Custom Block lists or feeds (or objects or groups) Block specific IP addresses, URLs, or domain names using a manually-created list or feed (for IP addresses, you can also use network objects or groups.) For example, if you become aware of malicious sites or addresses that are not yet blocked by a feed, add these sites to a custom Security Intelligence list and add this custom list to the Block list in the Security Intelligence tab of your access control policy. Reference: https://www.cisco.com/c/en/us/td/docs/security/firepower/623/configuration/guide/fpmc-configguide-v623/security_intelligence_blacklisting.html
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Custom Block lists or feeds (or objects or groups)
Block specific IP addresses, URLs, or domain names using a manually-created list or feed (for IP addresses, you can also use network objects or groups.) For example, if you become aware of malicious sites or addresses that are not yet blocked by a feed, add these sites to a custom Security Intelligence list and add this custom list to the Block list in the Security Intelligence tab of your access control policy.
Security Intelligence Sources ... Custom Block lists or feeds (or objects or groups) Block specific IP addresses, URLs, or domain names using a manually-created list or feed (for IP addresses, you can also use network objects or groups.) For example, if you become aware of malicious sites or addresses that are not yet blocked by a feed, add these sites to a custom Security Intelligence list and add this custom list to the Block list in the Security Intelligence tab of your access control policy. Reference: https://www.cisco.com/c/en/us/td/docs/security/firepower/623/configuration/guide/fpmc-configguide-v623/security_intelligence_blacklisting.html

Cisco Context Directory Agent (CDA) is a mechanism that maps IP Addresses to usernames in order to allow security gateways to understand which user is using which IP Address in the network, so those security gateways can now make decisions based on those users (or the groups to which the users belong to).
CDA runs on a Cisco Linux machine; monitors in real time a collection of Active Directory domain controller (DC) machines for authentication-related events that generally indicate user logins; learns, analyzes, and caches mappings of IP Addresses and user identities in its database; and makes the latest mappings available to its consumer devices.
Cisco Context Directory Agent (CDA) is a mechanism that maps IP Addresses to usernames in order to allow security gateways to understand which user is using which IP Address in the network, so those security gateways can now make decisions based on those users (or the groups to which the users belong to).
CDA runs on a Cisco Linux machine; monitors in real time a collection of Active Directory domain controller (DC) machines for authentication-related events that generally indicate user logins; learns, analyzes, and caches mappings of IP Addresses and user identities in its database; and makes the latest mappings available to its consumer devices.
Reference:
cda_oveviw.html
Cisco Context Directory Agent (CDA) is a mechanism that maps IP Addresses to usernames in order to allow security gateways to understand which user is using which IP Address in the network, so those security gateways can now make decisions based on those users (or the groups to which the users belong to).
CDA runs on a Cisco Linux machine; monitors in real time a collection of Active Directory domain controller (DC) machines for authentication-related events that generally indicate user logins; learns, analyzes, and caches mappings of IP Addresses and user identities in its database; and makes the latest mappings available to its consumer devices.
cda_oveviw.html