# ngrep > Filter network traffic packets using regular expressions. > More information: . - Capture traffic of all interfaces: `ngrep -d any` - Capture traffic of a specific interface: `ngrep -d {{eth0}}` - Capture traffic crossing port 22 of interface eth0: `ngrep -d {{eth0}} port {{22}}` - Capture traffic from or to a host: `ngrep host {{www.example.com}}` - Filter keyword 'User-Agent:' of interface eth0: `ngrep -d {{eth0}} '{{User-Agent:}}'`