Illegal host header , invalid host
Prometheus many invalid host metrics tag
Causes too much influxDB SERIES
For example,

curl http://127.0.0.1 -H 'Host: www.linuxhub.org'
curl http://127.0.0.1 -H 'Host: test'
curl http://127.0.0.1 -H 'Host: xxx'

Record a lot of invalid hosts