Enriching Data in Motion

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To enrich events with new fields from external sources (such as .csv files), we use Cribl Stream’s out-of-the-box Lookup Function. Ingestion-time lookups are not only great for normalizing field names and values, but also ideal for use cases where:

• Fast access via the looked-up value is required. For example, when you don’t have a datacenter field in your events, but you do have a host-to-datacenter map, and you need to search by datacenter.

• Looked-up information must be temporally correct. For example, assume that you have a highly dynamic infrastructure, and you need to resolve a resource name (e.g., a container name) to its address. You can’t afford to defer this to search time/runtime, as the resource and its records might no longer exist.

To use large binary databases (like GeoIP .mmdb files) for Cribl Stream lookups, see Managing Large Lookups. To achieve faster lookups, use Cribl Stream’s Redis Function.

Working with Lookups – Example 1

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Let’s assume we have the following lookup file. Given the field conn_state in an event, we would like to add a corresponding ingestion-time field called action.

action,"conn_state","conn_state_meaning"
dropped,S0,"Connection attempt seen, no reply."
allowed,S1,"Connection established, not terminated."
allowed,SF,"Normal establishment and termination."
blocked,REJ,"Connection attempt rejected."
allowed,S2,"Connection established and close attempt by originator seen (but no reply from responder)."
allowed,S3,"Connection established and close attempt by responder seen (but no reply from originator)."
allowed,RSTO,"Connection established, originator aborted (sent a RST)."
allowed,RSTR,"Established, responder aborted."
dropped,RSTOS0,"Originator sent a SYN followed by a RST, we never saw a SYN-ACK from the responder."
dropped,RSTRH,"Responder sent a SYN ACK followed by a RST, we never saw a SYN from the (purported) originator."
dropped,SH,"Originator sent a SYN followed by a FIN, we never saw a SYN ACK from the responder (hence the connection was 'half' open)."
dropped,SHR,"Responder sent a SYN ACK followed by a FIN, we never saw a SYN from the originator."
allowed,OTH,"No SYN seen, just midstream traffic (a 'partial connection' that was not later closed)."

First, make sure you have a Route and Pipeline configured to match desired events.

Next, let’s add a Lookup function to the Pipeline, with these settings:

• Lookup file path: $CRIBL_HOME/data/lookups/bro_conn_state.csv (note that Environment variables are allowed in the path).
• Lookup Field Name in Event set to conn_state.
• Corresponding Field Name in Lookup set to conn_state.
• Output Field Name from Lookup set to action.
• Lookup Field Name in Event set to action.

To confirm success, verify that this search returns expected results: sourcetype="bro" action::allowed. Change the action value as necessary.

Working with Lookups – Example 2

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Let’s assume we have the following lookup file, and given both the fields impact and priority in an event, we would like to add a corresponding ingestion-time field called severity.

impact,priority,severity
1,high,critical
2,high,critical
3,high,high
4,high,high
0,high,high
"*",high,high
.....
"*",medium,medium
1,low,medium
2,low,medium
3,low,low
4,low,low
0,low,low
"*",low,low
1,none,low
2,none,low
3,none,informational
4,none,informational
0,none,informational
"*",none,informational

First, make sure you have a Route and Pipeline configured to match desired events.

Next, let’s add a Lookup function to the Pipeline, with these settings:

• Lookup file path: $SPLUNK_HOME/etc/apps/Splunk_TA_sourcefire/lookups/cisco_sourcefire_severity.csv (note that Environment variables are allowed in the path).
• Lookup Field Name(s) in Event set to impact and priority.
• Corresponding Field Name(s) in Lookup set to impact and priority.
• Output Field Name from Lookup set to severity.
• Lookup Field Name in Event set to severity.

To confirm success, verify that this search returns expected results: sourcetype="cisco:sourcefire" severity::medium. Change the severity value as necessary.