The Art of Parsing
Raw strings become key-value pairs — cheaply, and at the edge.
Key takeaways
- Parsing extracts structured key-value pairs from raw logs using regex, Grok patterns, or native JSON extractors.
- JSON-native output needs zero regex parsing and saves massive CPU on the SIEM indexers.
- Do heavy regex work on the aggregation tier (Logstash, Cribl), not on the core SIEM.
Parsing is the process of breaking down a raw log string into structured key-value pairs using regular expressions (regex), Grok patterns, or native JSON extractors.
Take one SSH failure:
- Raw log: Failed password for root from 192.168.1.5 port 22 ssh2
- Parsed: action=failed, user=root, src_ip=192.168.1.5, dest_port=22
Two best practices govern parsing at scale:
- JSON is king. Whenever possible, configure your endpoint applications and forwarders to output logs natively in JSON. JSON requires zero regex parsing, saving massive amounts of CPU compute cycles on the SIEM indexers.
- Parse at the edge. Perform heavy regex parsing on your log aggregators (e.g., Logstash, Cribl) rather than on the core SIEM, to optimize search performance.
Parsing quality is invisible when it works and catastrophic when it does not: a field that fails to extract is a detection that silently never fires.
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