Hi,
It is the function of the rule 920350 that signals if you connect to the IP
SecRule REQUEST_HEADERS:Host "@rx ^[\d.:]+$" \
"id:920350,\
phase:2,\
block,\
t:none,\
msg:'Host header is a numeric IP address',\
logdata:'%{MATCHED_VAR}',\
tag:'application-multi',\
tag:'language-multi',\
tag:'platform-multi',\
tag:'attack-protocol',\
tag:'paranoia-level/1',\
tag:'OWASP_CRS',\
tag:'capec/1000/210/272',\
tag:'PCI/6.5.10',\
ver:'OWASP_CRS/3.3.2',\
severity:'WARNING',\
setvar:'tx.anomaly_score_pl1=+%{tx.warning_anomaly_score}'"