Grab user and pass ever plain http

tcpdump

tcpdump -i eth0  port http -l -A | egrep -i \
'pass=|pwd=|log=|login=|user=|username=|pw=|passw=|passwd=|password=|pass:|user:|username:|password:|login:|pass |user ' \
--color=auto --line-buffered -B20
click the source code to copy install tcpdump on any operating system with command-not-found.com