What I learned this month

Bro

https://www.bro.org/index.html

“Bro is a passive, open-source network traffic analyzer. It is primarily a security monitor that inspects all traffic on a link in depth for signs of suspicious activity. More generally, however, Bro supports a wide range of traffic analysis tasks even outside of the security domain, including performance measurements and helping with trouble-shooting.

The most immediate benefit that a site gains from deploying Bro is an extensive set of log files that record a network’s activity in high-level terms. These logs include not only a comprehensive record of every connection seen on the wire, but also application-layer transcripts such as, e.g., all HTTP sessions with their requested URIs, key headers, MIME types, and server responses; DNS requests with replies; SSL certificates; key content of SMTP sessions; and much more. By default, Bro writes all this information into well-structured tab-separated log files suitable for post-processing with external software. Users can however also chose from a set of alternative output formats and backends to interface directly with, e.g., external databases.”

Linux

getent hosts

bash -u

I should have know this, but bash -u finds undeclared variables for you.